I wonder if the poster means "Mainline" in the context of the East Coast Mainline and West Coast Mainline. Services to Scotland are, of course, operated on the West Coast Mainline. Perhaps the poster is confused by the operator, First Transpennine Express, which is probably one of the most poorly named TOC. Wether TPE should operate the services and if they have the right equipment is not for this forum.
What I would say, is that MAN is very lucky to have such easy rail access across the catchment area. Coming from Leeds city centre the time difference between the train to MAN and the bus/driving to LBA is very little. That makes MAN a viable option for many more people than otherwise might be the case. The flip side is that the comparatively difficult ground access to LBA and the operational challenges at that airfield make passenger leakage inevitable.