Remember what Scotty said in the Star Trek reboot - "Imagine that! It never occurred to me to think of SPACE as the thing that was moving!"
So to simulate a moving train, you just SSR the the train is in perpetual motion, and have all the terrain and units move in relation to it. Each Rph for the player who owns the train, all counters and terrain moves "x" number of hexes in the direction opposite the direction the train is travelling. Thus the train remains in the middle of the map, and the other units move in relation to it.
I'm sure you could fit such an SSR onto one card....