I have to agree with Dick. There is no technology, no system, that the Australian Government will not corrupt or allow to be corrupted in support of private profit or personal gain. Based on experience, there is no chance a universal SBAS based positioning system will be delivered as a public good to Australians at all.
The system will either be:
1. A prohibitively expensive 'for profit" subscription based business model developed by the financial leaches at Macquarie Bank.
2. A bizarre Australian implementation requiring special equipment at stratospheric costs to satisfy academic, defence and OH&S requirements unknown to the rest of the world.
3. A bean counters implementation providing services on a 9 to 5pm basis on the eastern seaboard.
4. A product of a "National Geospatial Commission" yet to be established, who will "roll out' the system at glacial speed over the next 50 years, a la NBN.
FFS give it to Dick Smith and some hobbyists and we will have a working system in 12 months.
To put that another way, buy it off the shelf and just do it.