Regarding title, I have been thinking about train tunnels and it dawned on me. A train arrives at a train station, mod removes train + content. Mod deploys a new train + content at a different train station. Clearly, this would be a workaround that imitates "Train goes in somewhere and out somewhere else". The tricky part would be keeping track of train contents (i.e. four trains quickly "entering a tunnel" (with high brakes) while spawning and accelerating trains slowly at the "exit")

This method could be abused (i.e. train spawns right at source and destination) but then again, players can mod and cheat their games how they want anyway. It is a bit silly I guess, but aside from having trains bounce on jumping pads, that's the closest it gets.