Motorizing Hobby Train 10183
The motor used in Hobby Trains is the 9V train motor. This motor is externally identical to the new Power Functions train motor, so you should be able to replace one with the other.

That said, the problem with Power Functions is that where in 9V it was enough to have the train motor mounted on the train, in PF you will also need to provide an IR receiver and a battery pack. You would need to modify each Hobby Trains model to have it house those components and the connecting wires (one of which should go through the floor of the train to the PF Train motor, so you need a hole in the floor). Net, it will require some creativity, and some Hobby Trains models are better suited to this adaptation than others.