OK Buzzbox the same department says this.
https://infrastructure.gov.au/aviati...apter_1.2.aspx
"CASA is responsible for implementing Australia's obligations under Annexes 1, 2,
6, 7, 8, 10, 11, 14 and 18 of the Chicago Convention"
Annex 6 being the key.
As a side note - a call on 121.5 is not only more likely to be heard, but also by aircraft that will record any important information said on a CVR. It alone may be a thing to save a few lives.