Not sure if this had been noted before, but I found that the link http://www.toiletmap.gov.au/ is rather helpful. I also managed to download the loos (state by state) onto my GPS (cannot remember the site but try "poi public toilets" in Google). Many of the toilets in National Parks also allow camping which was actually my prime reason for getting the POIs on my GPS.
I have also downloaded the waypoints on to my Tom Tom.Apart from the availability of a toot it sometimes is an indication of a suitable place for an ovanite camp that is not in the CAMPS NO--- book Cheers. Mary