I Assume its possible to run a steam train by cancelling or not scheduling 1 off peak train each way each day. Which is probably not going to make much difference to most off peak passengers.
If this were the case Scotrail would need to send 2 DMU's in multiple to Tweedbank to for the service that left Edinburgh before the stream train. One of these would make its normal return journey the other would need to wait at Tweedbank (with a crew) to form the return leg of the train cancelled to make way for the steam train. For the return leg the DMU arriving at Tweedbank before the steam train departed would need to wait at Tweedbank and join the following or later service in mutiple. Alternatively you need to cancel 2 trains each way,the one the steam train replaces and its return.
As far as running round at tweed bank is concerned there is no loop and 2 platforms so as far as I can see there are 3 options.
1 have a diesel at the end and drag the train back to Edinburgh
2 have a diesel at the end and use it to shunt the coaches into the other platform at Tweedbank thus releasing the steam loco for it to attach it self back to the other end
3 have a steam loco at both ends, not sure how this effects the 45mph speed limit for tender first operation, the loco on the end would be working as a banker.
Bear in mind that the journey needs to be done in 50-55 minutes to avoid mucking up other train timings,
the distance is 35 miles, with probably no stops, the DMU have to stop 7-8 times.
Discuss