Seems like the rules/legislation is changing fairly quickly
Some information about traffic infringements can be found here: http://www.rego.act.gov.au/infringements/infringedemerit.htm
Another place to check out is TAMS and Legislation ACT about rules, laws and policy: http://www.tams.act.gov.au and http://www.legislation.act.gov.au/
I "think" the new hoon law gives police the right to take your car if they think your a hoon. Generally things like really excessive speed, burnout, street racing will give the police an excuse to take your car.
My advice is to be polite and don't admit to anything unless they have evidence.