Bloggs,
It will be a CTAF (R) but that is still Class G airspace. As far as I know Transponders are only required in A,C and E airspace in Aus, as per
this
Has there been an instrument published to specifically require transponders be carried and operated in that airspace? If so where?
Dick,
That is positive news if true.
As to the criteria, there is now a published procedure requiring risk and cost/benefit analyses when deciding on Airspace classification. See the Australian Airspace Policy Statement 2007.