Normal limit is 110kmh. There are some remote roads posted at 120kmh. They run a demerit points system. A clean slate is 12 points. 19-29Kmh over is 3 points, 29-40Kmh over is 6 points, more than 40Kmh over is 7 points. Lose 12 points cumulative in any rolling 3 years is an automatic suspension for 3 months.
If you are being really stupid, careless , reckless or dangerous driving or more than 45Kph over the limit , they have the power to confiscate your car upon conviction for 28 days. If you are found to be reckless driving three times within a 5 year period the police can apply to have your vehicle crushed.
This always gets the press excited with pictures of some extreme modified rice burner before and after, and some sad looking idiot thinking about walking everywhere for the next six months.
In my experience if you are stupid in a vehicle you are more likely to be punished by the roads , environment and the wildlife than the police on remote roads . That will punish you allot more than the cops.