As pointed out previously, there are Motorola Smartnet Trunking systems in the Brisbane area. Just scan between 865.0125 and 869.9875 MHz in 25KHz steps, and listen for a continuous data transmission, and try that frequency as a Control Channel. The Control Channels rotate daily (ie. freq A is used one day, freq B used the next day, etc, up to four freqs). Unfortunately, scanners made for the American market have the 800 MHz band blocked above 868.9875 Mhz, so that may be a bit of a problem.
There are at least two active Sites on Mt Coottha.
There is an 800MHz EDACS system at Gladstone (Boyne Island Smelter)
There are supposed to be some LTR systems in the Brisbane area, but I don't have the equipment to listen for them. There are some ComGroup and Vertel frequencies on Mt Cotton that are possible candidates. Scan between 478 and 510 MHz. Google to find out what to look for in the way of an LTR Home Channel.