Hydraulic cylinders?? I wish!! Nope, I'm afraid the steering is all down to good ol' human power. As was mentioned before, the machine articulates in the middle - there's a pic below of the linkage on my machine.
There was a machine built a couple of years back that had the trailer wheels steering as well as the middle being articulated, but the owner has not been seen out on the track since it's first trip out, and I've never seen it in action.
Transmission is via a torque converter - this class of mower (in the UK) is the only one where a converter can be used. #25 is based on a Hayter Condor - and mine (the black #7) is based on a Scag SWZ.
Any more info you need - just give us a shout!