Squawk7700,
Some airports require it for all areas airside.
With very few exceptions, if there is an ASIC display requirement then it applies to all areas airside. I seem to call Moorabbin had a specific area at one time when they had RPT operating out of there that required you to display an ASIC.
Some airports require it to be displayed within the blue line area(s).
That was a home baked solution to get around the screening requirement of non-RPT aircraft departing off the same apron. CASA didn't like the practice of non standard apron markings being painted and the change in reqs back in about 2011 there was not longer a need for it.
Certain areas require it to be airside within a certain timeframe either side of an RPT arrival.
That exemption applies to airports that do not have screened RPT services. The "Traffic Period" is two hours prior to the arrival until two hours after the departure of the RPT service. Creates an interesting question where the airport operators Transport Security Program might say a person has to display an ASIC at all times yet the regs allow for something else. Would be a good argument you could have with the airport staff if, on the unlikely chance they ask "where is your ASIC" and you say you are operating within the provisions of Regulation 3.03(4a).