UP's rotaries are diesel-electric. In the older one, the engine and generator feed 4 traction motors which turn a large bull gear. That, in turn, goes through a reduction gearbox, the output of which turns the wheel.

UP's newer plow, the one they've been using lately, is slightly different. There, the engine and main alternator power one large electric motor, which runs a reduction gearbox, thence the plow wheel.

I have seen internet claims that the engines in these plows turn the wheels directly, which is ridiculous; the plow wheel could never stand that high rpm (900+) without flying apart, and the only way to change the direction of the wheel would be to kill the engine and then make it run backward.