I made a quick mini-mod of it so you can easily load it into 3dsmax. The locomotive model was made by smig a long time ago, you can dl his free models here: http://www.smig.name/
To keep the train on track I modified fo0k's idea a bit since the train would often derail on the (unrealistic) sharp Vanilla bends. What you see in the mod is about max speed without derailing, if you want more you have to create new wider curves or slow down. Some vehicles have problems crossing the rails, Sherman and PanzerIV go over it at any speed no problem but the T34 is really struggling when you drive very slow.
The most difficult thing was the coupling, I tried a lot of ideas with rocket engines but that usually ended in a disaster. Then I suddenly had a different very simple idea and it worked right away, I'm not very good at explaining stuff so check it out in the code/3dsmax.

One thing I have to mention though: There was also a problem that wagons would often unhitch when I started the train after a short stop. Vehicles go into a "sleep mode" when you leave them alone and because of that they ignored an important collision mesh (Train_Puller) which is why I couldn't pull them anymore. I fixed that by adding a rocket engine with 0 torque to keep them always "active". But Rocket engines stop when someone occupies the related PCO or brings the vehicle below critical damage so I had to create a sepperate PCO which cannot be entered. Overall maybe not the most elegant solution but it works.
If you have any questions ask away I'll try to help.

btw. you can unhitch the wagons with the up/down keys as train driver.
Download: https://drive.google.com/file/d/0ByT8vo ... sp=sharing
Edit: Train is placed on Stalingrad for testing