If you look carefully here right end of the coach on the right you can just about see the exhaust silencer of the engine
http://www.platform11.org/images/22000/image_3.jpg
Each coach has a 520hp MTU engine good for 100mph
The only time these will need a locomotive in front is on the way from the docks to the depot. That said IE hid the locomotive this afternoon when the bus full of IE heads arrived and I mean bus as in double decker