The Scotsman’s second Google Hangout discussion on the scheme will feature infrastructure secretary Keith Brown debating the scheme with rail consultant and author David Spaven, one of the leading authorities on the railway.
Locals who have won a “Golden Ticket” to travel on the line will take part in a series of preview trips on Saturday, ahead of the public opening on Sunday.
The Queen will travel on a steam train to officially open the route on Wednesday, 9 September.
The line forms the northern third of the Waverley route between Edinburgh and Carlisle which was closed as part of the Beeching cuts in 1969.
ScotRail trains will run between Edinburgh and Tweedbank, just south of Galashiels, calling at seven new stations as well as the existing Brunstane and Newcraighall stops on the south eastern edge of Edinburgh.
The live discussion will take place at 12:45pm