Yes there is definitely some cool rail equipment out there. Have you seen the Brandt OTM Tracker? Basically a Deere Excavator with a purpose built undercarriage to move on top of gondolas.
http://www.brandt.ca/Divisions/RoadR...9&cat=Products
There's a bunch of videos of it on Youtube, just search for OTM Tracker. Here's one:
https://www.youtube.com/watch?v=zNbd8Z-9JUo
Brandt also makes a tractor/power unit for moving railcars, etc. I considered making some of this stuff but then you'd also have to build the railroad, so it's not high on my list. Hope this helps.
[Normal disclaimer: I don't work for Brandt, nor am I trying to advertise their product, blah, blah, blah]
Oh! One last thing, check out the Herzog car toppers. These guys get backhoes up on top of gondolas. Way cool! Bet it's scary as **** learning how to do it right.
https://www.youtube.com/watch?v=j0ddhTvMwSQ