In the FAQ, Mal states that he had worked on train support but does not say how far along it had got. Basically unless Mal finds time to work on FritzBot again or transfers the code development flag to somebody else then No.
To sum up, this is what vehicle behavior FritzBots have;
1) Only one vehicle has active focus at any one time.
2) Vehicles are assumed to be vulnerable to damage
3) Only one team owns the vehicle (can move it) at any one time
4) Only the team that owns the vehicle mans the mounted gun (if any)
5) Vehicles are assumed to be high priority to game objectives.
6) The team that does not own it will use grenades, satchel, panzers and air cans to destroy it when near enough.
7) The bots that own it, try to get to the vehicle's script trigger to move it from the node nearest to it (or is that nearest to the script_mover?).
Now waypointers like Crapshoot et.al. have found ways to partially adapt to these limitations by;
7a) Moving the vehicle one stop at a time along its sometimes 100-200 splines/markers so that the nodes and connections are optimally placed so the bots approach only from the right direction, to trigger movement, do repairs etc. This approach might also be used to direct bots into a restriction like a cab BUT ONLY WHEN THE VEHICLE IS STOPPED. Bots can't calculate how to get inside a moving vehicle.
7b) Re-scripting (if possible) a new movement trigger to change its location and trigger area. In this way for instance, bots may move a vehicle just by getting close enough to the to outside (like the trains in __Bridges__)
Now it might be possible to figure some way to swap the bot ownership behavior in Railgun but it would be arbitrary (like who owns the CP, or which team last got close enough to trigger movement). And I suspect that the team that got to the train first would likely "own" it for the whole game. The other problem is that the attacking team would try to damage the train and since it is invulnerable, waste grenades, satchels, air cans and do lots of team kills (like in my Supply Depot 2 and 3 waypoints).
So with current behavior waypointing Railgun would be a lot of work for a less than mediocre result (the challenge would be interesting though). If you want to play with trains, Bobots can operate the train in Railgun but even then they are nowhere near as good as humans.
As to non-objective script_mover (trams, skycars, monorails, blimps) as well as gliders I have had some success not declaring them as vehicles and inducing the bots to use them by path restrictions in combination with fake toi-func_construct interactions between the aiscript and the map script. But even here (see glider 3.02, eagles2ways, northpole, airassfp1) the bots are never as efficient as humans.