The RTA rule of 49cc or 200w was pretty much made irrelevant in mid 2009 with a case in the NSW supreme court. The was a case where a woman in Broken Hill was charged while on an elecrtic motor scooter that also had peddle power. The Supreme court ruled if it could be shown the vehicles primary form of propulsion was the motor than it would be classed a motor vehicle irrespective of power and thus all relivant laws for motor vehicles apply.
I can tell you this is easy for police to prove. Follow the motorised bike and observe if the rider is using the peddles. I've even come across bike with the no drive chain from the peddles only the motor.
Funniest one I have seen is a small childs trike which had a wipper snipper motor mounted on the handle bars powering the front wheel, peddles had been cut off replaced with foot pegs. Rider went unregistered, uninsured and disqualified driver. He took it court and lost.
