The union has served notice of a potential strike amid an on-going pay dispute with operator ScotRail.
The union said that the schedule for the ballot would enable action to take place during Cop 26 if members were to back the motion.
Earlier this month, RMT had threatened such action that will now see over two thousand members across all grades are involved.
RMT General Secretary Mick Lynch said: “Today's ballot announcement has been forced on us by the deliberate time wasting by ScotRail and Transport Scotland.“This issue should have been sorted by now and we should have had a fair and just offer that recognises the hard and important work of our members.“The union will be campaigning for a massive yes vote and we remain available for talks.”
ScotRail has yet to announce its Cop26 trains plans however extra late-night services on Edinburgh to Glasgow had been planned
"Extra late night trains will operate on the main Edinburgh-Glasgow route throughout the conference.
ScotRail has yet to announce details, along with plans for additional services and/or longer trains on other lines such as to Exhibition Centre station beside the SEC."
A ScotRail spokesperson said: “It’s extremely disappointing that the RMT have opted to ballot for this highly damaging strike action, particularly when talks are ongoing.
“Although we are starting to see customers gradually returning to Scotland’s Railway, our financial position is precarious and strike action is wrong at a time when we need to deliver a safe and reliable service.
“We need to provide stability for our staff and customers and RMT is wrong to take a ballot of disruptive action instead of working with ScotRail to address the grave long-term challenges facing the rail industry.”