I think the Foreign Pilots here need to remember that Australia isn't exactly blessed with a large number of Major Airports to land at all over the place, especially when you're talking Jets, there's a lot of extremely empty countryside out there.
My personal question is, Why did CASA see fit to change this rule? They carry on all the time that they're doing everything for safety and to increase it but this seems like a step backwards? You'll always have operators who push people into taking the minimum required fuel and they now have set that minimum even lower. I don't think the problem is so much with the RPT side of things, I think the big issue will be with GA personally, Pilots at the lower end are under much greater pressure and lower margins with bosses that don't always care as much as they should.
I honestly don't think they'd have anything to back themselves up with in terms of data to show that this will have no impact on Safety for GA or indeed even RPT. Large Jets/RPT possibly, as their figures are much better tracked and there would be plenty of reliable data to be taken from Operators to show what effect this has but at the GA level I think they would have no indication whatsoever and this is what really annoys me about these decisions is the lack of any real clear decision making rationale from CASA and the lack of any reported Data or Research that backs them up in regards to it. They should be held accountable and required to release their research into the impact of these changes beyond simply stating "ICAO", ICAO are there to give us recommendations and we are meant to take them and check if they're applicable to our country and how things work, not just blindly follow them.