My experience working there is limited to the Bathurst 12 hour event featuring the Australian GT series, for which I was put in touch with a Queensland couple that organized marshals for that event. It is my understanding that V8 Supercars organizes it’s own marshals for the Bathurst 1000 which is probably the biggest event on the Aussie calendar.
My first visit to Bathurst was long before I started marshaling in 2009 when I lived in Australia. In fact I paid a visit to Mount Panorama with friends from the Blue Mountains that took me there before I knew anything about that circuit. Since it is a public street I was able to drive on it then, and a few other times when we organized FPV cruises to the famous track.