I think its best to have it with you but when I got mine (Im in Victoria) i gave the lady it and she never looked at it. I drove around for just under a year on my UK license-which you can do as long as you are not there permanently. I had to get a Victorian license as im likely to have to drive a government car for work (i work for the government now) i then bought a car and needed a license for actually buying the car. It is possible to buy without an Oz license but it is easier with one.
Again this is just for Victoria. The best place to look for info is the road authority for the area you plan on being in.