It's not
I've got a review copy here - it's a kind of strategy game. It's quite pretty and in full 3D but essentially it boils down to the following:
There are a number of entry and exit points and stations. There are also numerous points.
While playing a level your job is to build up a certain score, you get some points for getting a loco through all its jobs (e.g. it arrives and is held at an entry point, it has a work order represented by icons above the cab such as "stop at green station depart through blue tunnel", you then have to set the points and clear the signal to let it run, making sure you set the signal on the station so it stops.
Each train has a random work order and they start to happen at the same time, your job is to clear them as quickly as possible which can mean some juggling. If you take too long between 'completions' then you lose a point, and continue losing points periodically.
Personally after a quick run in the game I found it very frustrating and i'm only on the first level! Maybe i'm just dumb?
Some initial comments:
It uses the same portals sometimes for entry and exit, which means you can have a train almost through to the exit portal when suddenly another train appears and screws it all up. There may be a way to improve this though, not sure.
There are only signals (so far, that i've seen) at stations and the entry point - so you couldn't even say this is an attempt at a simple signalling simulation (which might have been more fun). Once you start a train on its way I am not sure if there's any way to stop it, but i'll find that out before I write the review of course

What i'd like to have done is let it in to a particular section and have the trains simply running section to section - but you can literally have them tail-chasing or crashing in to each other quite easily if you're not careful.
Overall so far (after only an hour or two) it's well presented and has potential - I'm just hoping that further experimentation will help iron out some of the quirks i'm having with it - if not then it's seriously flawed imho.
Matt.