The wintry weather last December and January delayed progress on the Airdrie to Bathgate rail link by five weeks as frustrated contractors were unable to carry out construction work on the new line.
"People were telling us that we would never finish on time following the snow," McAulay recalls. "They were saying there was no chance of catching up."
But, barring any worsening of the weather, the link will open on time and on budget next Sunday, although the "official" opening on Friday - with politicians and local school children - has already been cancelled because of the weather.
"We've been running trains on the line for the past six weeks," explains McAulay, who joined Network Rail in 2003, a year after the not-for-profit company was forged from the ashes of RailTrack. He has overseen the Airdrie to Bathgate line since its inception. "Apart from some car park surfacing work and putting up some signs, we're just about there.
"You can't imagine the pride I feel in this project," he beams. "I feel pride in all the projects we've completed but this one is special."
Work on the 53-kilometre line began in 2008, with the 300 million bill being picked up by the Scottish Government. While Network Rail has budgets to maintain and enhance existing track, any new lines in Scotland are funded through the public purse.
But how did McAulay and his team complete their project on time and on budget when the landscape of public infrastructure projects is littered with so many failures?
"The 'mother's homemade apple pie answer' is hard work," says McAulay.
"But it's also about team work between ourselves as project managers and our contractors, including Balfour Beatty, Carillion and Scott Wilson.
"We set up a steering group, which sounds like it's just another committee but it was a working group that aired problems as they arose and found solutions rather than letting them fester."
McAulay emphasises that the Airdrie to Bathgate line isn't the only project that Network Rail has delivered on time and on budget; he quickly reels off the Larkhall to Milngavie link, work on the Lugton loop and the construction of two additional platforms at Glasgow's central station as other success stories.
The new electrified line will cut journey times from Airdrie to Bathgate to 45 minutes, running from about 6am to about 11pm. The service will stop passengers from having to travel into Glasgow or Edinburgh to get a connecting train between the two cities as trains can now run direct.
The line was closed to passenger services in 1956 and freight in 1982. The Bathgate branch line linking the West Lothian town to the Scottish capital was reopened in 1986 and formed the basis for the new rail link.
Economic impact assessments estimate that each pound spent on the line will deliver a return of 1.81 over the next 60 years by boosting local businesses.
Sam Crawford, a director of Enterprising Bathgate, which runs the town's business improvement district (Bid), says companies in the town are already gearing up for the extra trade that the line will bring into Bathgate.
"The line will give us direct access to customers in North Lanarkshire for the first time in a long time," says Crawford. "But we're also seeing this as an opportunity to attract new businesses to set up in Bathgate. The improved commuter link is just one of the steps being taken to revitalise the town, with the opening of a new council building next year also creating about 150 jobs."
Iain McMillan, director of CBI Scotland, is also convinced of the economic case for improving Scotland's railway infrastructure.
"The Airdrie-Bathgate line doesn't just open up new opportunities for people to travel to work or college but it also forms a connection for the electrified railways in the north of Glasgow all the way through to Edinburgh Waverley.
"Electrifying the main Glasgow Queen Street to Edinburgh Waverley route now needs to be the rail priority for Scotland. It won't just cut journey times and allow more trains to run on the line but it will also be more environmentally friendly by cutting the amount of carbon dioxide produced by the diesel trains."
The 1 billion Edinburgh-Glasgow Improvement Programme (EGIP) - which would include the electrification of the route between Scotland's two largest cities - was protected by John Swinney in his Budget, alongside other transport infrastructure projects such as the Aberdeen peripheral route and the completion of the upgrading of the "missing link" stretch of the A8 to full motorway status.
McAulay said he recognised the project as being the priority for Network Rail in Scotland now that the Airdrie to Bathgate link has been completed.
He says the scheme would allow 13 services per hour to run between the two cities, with journey times cut from the present 50 minutes to about 37 minutes.
"Electrifying the central belt would also let us put more trains on routes to Alloa and Dunblane," McAulay says.
"Eventually, we would like to see electrification spreading north to Perth and then Dundee and Aberdeen."
The process can't come soon enough for many industry watchers. Jim Hunter, a lecturer in civil and railway engineering at Edinburgh Napier University, worked as a principal engineer for design firm Scott Wilson on the Airdrie to Bathgate line.
"Electrification of the Edinburgh to Glasgow line was talked about back in the 1980s," he says.
"But it was shelved because of the recession in the early 1990s and the privatisation of the railways."
While he welcomes the moves to make progress on EGIP - which is due to be completed by the end of 2016 - Hunter believes the Scottish Government also needs to be thinking in the longer term and should be pushing for a high-speed rail link to London.
The Westminster coalition government has committed itself to building a high-speed railway - with trains reaching 300 kilometres per hour - from London to Birmingham and then on to the north of England. The line could cut journey times from Scotland to London from more than four hours to just over two.
"The Scottish Government needs to be much more vocal in lobbying for the high-speed link to be built to Scotland from the beginning of the project," Hunter says. "This needs to be the next rail priority.
"If it's not then it would be harder to add the link at a later stage and the economic case for building a high-speed line requires the track to go to Edinburgh and Glasgow to get people away from air travel."
McMillan echoes Hunter's assertion that high-speed rail needs to be the top focus for governments north and south of the Border.
"It's time for the UK government to put its money where its mouth is," the CBI director says. "It needs to commit to extending the line to Scotland. We're a united kingdom after all and we should all benefit from high-speed rail, not just cities in the north of England."