The issue over it being a cost and staff reduction is far fetched, it is more about providing the safe level of service to a rapidly increased amount of traffic with no surveillance at all. Unlike the USA with Radar everywhere, we don't and won't. This is about giving the controllers at the coal face the tools needed to handle the increasing volumes in a more congested space. Radar or ADSB will do it, take your pick.
Capt12am
Flight radar24 and the like take feeds from plane spotting PC users who have an ADSB receiver on their roof and provide the data live via the internet to the FR24 site.
They will not have anywhere near the coverage in central Australia that ASA have due to the lack of techno nerd plane spotters in the GAFA.