Noted by
S_W_S
There is a rebooking allowance for NCL and EDI usually on LNER anyway, so BA agents were able to rebook on to the train for cancelled flights. However, this seems much easier as you presumably just show your cancellation email on the train and don't need to contact BA or go to the effort of paying and claiming the cost back. I guess you could use this for GLA, ABZ, and INV as well or wherever you were heading on the east coast line.