Thanks guys. So bottom line is with a little creative reasoning, while not at all common, it would not be unheard of to have such a train run on the Terminus I plan on building.
I plan on making it war/post war period, so in my little background I imagine them possibly being used as evacuation trains, or bringing soldiers home. With that, I think under the circumstances, it would work and I could use a "for the war effort" attitude.
I had just purchased a Hornby Wellington Castle, so with its livery it puts in right around 1945ish. I'll just say it got its running in taking Soldiers home or something to that affect.