Stupid thing is, you can learn in one, because a fully licenced driver is "in charge" of the vehicle. All well and good, but who's "in control"? And then, you can drive to the test, and do the test, in one, but (assuming you pass), you can't drive it home!!!!! Yes, it's based on the power : weight (125 kW / T) (or capacity : weight = 3.5 l / T), ...BUT.... Initially, cars are placed on the list according to the factory spec. But, if you hot up a car not on the list to a point where it exceeds to power : weight (or capacity : weight), then it is also "technically" illegal for a P-plater do drive it. So you stick a 5.7 V8 in a HQ, then it's illegal for a P-plater, even though the stock HQ is legal.