Creampuff, I don't have time to write a proper response (especially to Dick) now, however,
I see no point in Australia spearheading a technology that may turn out to be a unique and therefore unnecessarily expensive orphan
Given that the money for this technology is going to be pissed away anyway (maintaining/replacing old radars), why not accept the 'experiment'? If the world goes another way (ala DME) then change in the future- but the world will be learning from us and the benfits flow immediately to oz aviation in having ADS-B NOW. If the problem is that; if, in future, a system change is required, owners fear that AsA wont pay for it, then just have that rider put in now. With the pace of technological change, trying to go with "what's best" appears to be a futile exercise in naval gazing and procrastination.