Just because you've seen one on the road with P's doesn't mean it was legal (it might not be), or that you can also have it (they might have an exception from their RTA). There ARE exceptions to the rules. If you owned the car before the rules came into effect, or its the only car you have access to, etc. So call your local RTA to discuss.
This is for the Coupes. Sedans with the smaller engines might be fine.
Illegal in NSW
P1/P2 licence holders are also restricted from driving the following 6-cylinder vehicles:
BMW M and M3.
Honda NSX.
Nissan 350Z and 370Z (including private or 'grey' import variants eg. Infiniti G35, Infiniti G37, Skyline 350GT (V35), Skyline 370GT (V36)).
All Porsches from 1994 models onwards (except diesel).
Mercedes Benz SLK350.
Illegal in QLD
A high-powered or performance vehicle is defined to include a vehicle with any of the following:
of more than 200kW under the manufacturer's specifications for the car
Probably Illegal in Victoria. Not sure as their current list is down. Call to find out.
Their old list had the 350z on it.