Possibly it is the same motor, or very similar. I think the tank engines had a generator running out the back end of the motor, where this one, I believe, had the generator up top at the engine front.
Here is a link to one, new out of the crate, for sale on the UK craigslist. Wrong side of the pond, or I would be on that tomorrow:
http://edinburgh.craigslist.co.uk/ptd/3895747649.html