As a model railroader that's pretty cool. Depending on the price I would get one just to put in my train room in the basement where I have collectible railroad stuff from signs to lanterns and other railroad memorbilia.
Some motherboard have on-board power supplies (at least the Atoms that we've used for embedded systems) and only require a 12V DC input.
You could liven each track (one 12VDC the other GND) and power the PC through the wheels.
Combine this with Intels Widi and a Wireless mouse Keyboard, and yo wont need any wires!
Does anyone know if you can get a Mini-ITX motherboard with Widi?