Update September 2000: I have had a few questions over the past few days regarding "Open Channels"
I'll do my best, if anyone else has anything to add, let me know.
There are 3 "Total Area Coverage Channels" also known as "Open Channels" - these channels are used when officers need to speak to each other direct, and are not close enough for channel 2 local (467.875). Open Channels are also used at major sporting events, large protests or similar.
Here are the channels, and a list of the areas they cover:
Channel 24 (468.425) - I, J and K Districts
Channel 45 (468,950) - F, G and H
Channel 48 (469.025) - D and E
* A, B and C districts can chose any of the above channels.
Here is some infomation I collected while in the city last week:
Channel 2 local - Used for normal simplex car to car communications.
Chaannel 3 - Used by Yellow units at the soccer at the MCG. Which was later controled by Hotel 900 which was at the Hilton, the units were awaiting the arrival of the players and refs.
Channel 24 - Used by units directing traffic around the MCG.

Channel 24 is presently being used at the Royal Melbourne Show, and operators are directing units searching for a "Open Channel" to channel 45.

Update: On the 29/11/99, the Victoria Police implemented their new districts. So far the new districts have had little effects on people who monitor the Police frequencies. The only change that I am aware of is that some stations have moved to their new districts. As you would be aware not all stations will be able to move (in reguards to their radio communications) to their new districts, because of the repeater locations.
In this update I have been able to make some amendments to the districts & the frequencies they are now using. If you have any more information that may be useful please send it to me.