Is Australia a ICAO member?
http://www.icao.int/APAC/Meetings/20...%20-%20rev.pdf
5. ICAO requires that all aircraft monitor 121.5 at all times in areas where ELTs must be carried (which includes the whole of Australia).
6. ICAO recommends that all aircraft monitor 121.5 at all times to the extent possible.
CASA is responsible for implementing Australia's obligations under Annexes 1, 2,
6, 7, 8, 10, 11, 14 and 18 of the Chicago Convention