It is not uncommon for model aircraft clubs to have CASA approvals to operate within a certain area above 400ft AGL.
Typically the ERSA for the closest airfield will be updated with model aircraft listed as a hazard and their location and maximum height.
The issues you will run in to with requesting radio calls is that the aeromodellers will need to hold an AROC to broadcast on 126.7. Handheld Airbands are usually pretty average in their ability to transmit from the ground up too
There is little to no chance of model aircraft being approved to use a transponder or conspicuity device.
In the drone world CASA will only approve the use of a secondary surveillance radar (SSR) or an automatic dependent surveillance broadcast (ADS-B) transponder (electronic conspicuity (EC) device) if it is required for the duration of a drone operation, subject to CASA assessment, in the interest of air navigation safety. In general, approval will only be issued to BVLOS operations above 400 ft in non-controlled airspace, BVLOS operations in controlled airspace, or other operations that are integrating with crewed aircraft and require ADS-B out for separation requirements.
The MAAA run the model aircraft regulations and there is no avenue to use a transponder under their regulations
In Vic I know Werribee MAC, P&DARCS and PARCS have 1500ft AGL approval, pretty sure VARMS does as well, Greensborough MAC have 900ft.