You are aware of the Australian system, aren't you?
Naaahhhh!!! What would I know about the Australian system ---- after only fifty odd years and tens of thousands of hours, flying from the damned nearest the smallest to the largest, and many hundreds of hours sitting on various consultative bodies, from prior Airspace 2000, to every iteration since.
If you can't work out the differences for yourself, I can't help you --- have a look at the references I posted, then consider what aircraft/operations the Australian mandate applies to.
The highest utilization ADS airspace in the world I think is between USA and Europe where there is little radar coverage.
The North Atlantic MNPS area is one that is/will greatly benefit from ADS-B, unlike airspace with current radar coverage, where US airlines have largely been unable to find any benefits/savings that justify the capital expense. Anybody who doubts this --- Google is your friend -- there is plenty on both sides of the arguments published, start with the ATA.
Tootle pip!!