Dick
Could it be something to do with ASA trying to find a way not to spend the $$$?
As for Tasmania, probably the reason ADSB is not being used there is because until the full fleet is fitted, both the smaller RPT and GA, the ADSB screen would be blank!
If they just did the whole thing and did it properly, put systems in place to ensure integrity, I am sure all would be better off.
J