Maybe the Aussies have it right, and the requirements were not well substantiated in the first place, particularly for long haul airliners who tend to fly under radar control or under well established flight routes.
The GA event presented as the trigger hardly fits the "we know where it is or will be" model of an airline flight. I can see how an ELT is a good idea when you fly in out of the way areas, or typically in uncontrolled airspace.
I'd be interested to hear what people in the SAR community, civil and military, think about ELT's as an aid to their making first contact with a downed aircraft.