RNP AR is not an Aussie thing. It is the ICAO form of FAA RNP SAAAR.
The AR is Approval Required which is that it is not a public use approach. The operator is approved for specific aircraft type and specific pilot training requirements. The RNP AR approaches are usually a "tailored approach design" for a specific aircraft type. An AR approach for a B737CL may be slighty different to the same approach for a B737NG. Public use RNP AR approaches are built with a lot more "fat" for want of a better term to allow for different aircraft capability.
Only six to nine leg types are used for AR operations one of which is the RF leg. GNSS updating is usually the chosen sensor for RNP AR however with good DME DME updating a RNP 0.3 RNP AR approach is possible. To go lower than RNP 0.3 then GNSS is almost mandatory.