From the Airservices website:
It’s objectives are to provide additional safety, efficiency and flexibility to airspace users through the wide-scale deployment of ADS-B technology.
If a significant percentage of aircraft operating in Australia were capable of transmitting ADS-B data (ADS-B Out), it is expected that:
a) Airservices Australia, and therefore its customers, could avoid the expense of maintaining existing enroute ATC secondary surveillance radars.
b) Regional airlines and others could decrease costs and increase safety by being able to electronically support “enhanced see and avoid” operational procedures. These aircraft would require the capability to receive ADS-B signals (ADS-B In) for display of traffic on cockpit displays.
I understand that it will be cheaper to install the necessary ADSB equipment in all VH registered aircraft than to maintain the current SSR radar sites.
More information on the project can be found at
http://www.airservicesaustralia.com/.../adsb/adsb.htm