Got an answer from ACMA. “Basically it may be in the radio station’s best commercial interest to maintain the technical standard which is most accessible to the audience. However as it is not part of the broadcast license condition, it is outside of ACMA’s remit which encoding technology a station choose to broadcast on.”
Interesting eh? I wonder if it should be like this. When the radio does not work people tend to blame digital radio rather than the broadcaster. Happy they responded though.