This does of course not mean the end to your scanning hobby. It means you mearly have ot change some of your listening habits, and go looking for other users who are interesting and use analogue. Considering the police are only one of serveral thousand radio spectrum users in Melbourne, you still have a huge choice of things to monitor. Part of the scanning hobby is doing a bit of detective work. Try searching out users like security, private investigators and various inspectors from all forms of government, as well as other interesting things, like trunking systems ( Melbourne has a stack of these ), airband, marine band C, amatuer, commercial and so on and so on. The listing is endless, you just have to put your mind to it.
One thing I used to like listening to in Sydney, before they scaled down their radio system to a low powered system was Star City Casino security. Made for some interetsing listening, specially when you worked out what some of the call signs were.
I am not sure what Crown Casino uses, but casinos are havens for crime, and they have some of the most sofisticated security system in the world in casinos. This might be a place to start.