the ROI on that kinda stuff is pretty high, if you brought this out when GPU mining first started it would be worthwhile, but now with the advent of ASICs which run off low watts, its not all that valuable of a service.
The amount of electricity it generates doesn't change based on what it's running. Watts are watts, be they ASIC or GPU or FPGA.
I'm not in Australia, but I think it is a great idea.