They have had to battle snowdrifts and temperatures of -15C during the work to keep trains running on the world’s most scenic line.
Ageing radio equipment which controls the West Highland line between Glasgow, Fort William and Mallaig is having to be replaced because their frequencies have been reallocated.
The site near the summit of Meall a’ Bhuiridh above the Glencoe Mountain ski area is one of 23 hilltop locations for signalling masts along both that route and two lines north of Inverness.
Network Rail and specialist contractors Telent Technology Services have had to use a snow tractor, mountain guide and even a skiers’ chairlift to help reach the site.
Pictures show them using ice axes to access a frozen building.
The work involved removing a one-tonne base station by helicopter last August, with a replacement being installed over the following month.
Network Rail spokesman Nick King said: “Engineers have been continuing to work on the project throughout the winter using the helicopter to transport equipment when possible, although this has been affected by snow and wind conditions.
“The Glencoe snow tractor has also been used when the weather was too poor to fly. They’ve even used the ski lift on occasion.”
“The last of the equipment will be moved from the old base station to the new one this weekend.”
Stephen Pears, Telent’s rail managing director, added: “We have engaged the assistance of a local Glencoe Mountain guide to allow us to safely access the summit of White Corries under expert supervision.
“Teams also carry personal protector beacons to alert the mountain rescue in case of emergency when working at remote hilltop locations.”
Signalling on the rail lines is different from the rest of the Scottish network, based on radio links between signallers and train drivers rather than lineside colour light signals.
Known as Radio Electronic Token Block (RETB), it involves signallers giving drivers a virtual “token” which lets them proceed safely along sections of the single-track routes.
The system was installed 30 years ago because it was half the cost of upgrading the traditional signals. However, the radio frequencies it uses are now needed for digital radio and television.
New equipment is also being installed in drivers’ cabs and at the control centres at Banavie and Inverness.
Friends of The West Highland Lines chairman Doug Carmichael said: “RETB signalling, which commenced in the 1980s, has always brought a new dimension to operating Scotland’s rural railways, especially through the glens and on the West Highland lines.
“Once, trackmen battled through snowdrifts to free signals and their wires to remote signal boxes.
“Now, engineers climb mountains to obtain the best possible transmissions for train safety – still battling snow!”