This is one of those questions that always seems to spark debate.
Viewed from a strict legal perspective, based on the assumption that our equivalent of the UK OFCOM (which we call ACMA) has not laboratory tested your radio and found it to be suitable for use in Australia, then it is not considered ACMA "type approved", and only ACMA type approved radios can be used on the UHF CB band under the ACMA UHF CB band "class license".
Viewed from a practical perspective, the answer is that there are many people who use non "type approved" radios on the band and there seems to be little or no action taken to deal with this
I have been bringing ham radio gear in and out of Australia on frequent occassions for 5 years and never been quizzed at customs. Also had police ask out of curiousity what I was doing while operating ham gear stationary mobile and never once have they asked whether it is a CB or "type approved"?
Just listening to some of the action on the CB bands, particularly in the cities, suggests that ACMA either does not monitor them much, or if so, does not put much emphasis on enforcement.
Just my views and I could be wrong.