They put similar no fly's over just about every serious event these days, stops drones and media getting in the way of airborne police assets, not unusual, I've had to change runways once due to a domestic dispute siege in a house under one approach path. The only unusual part is being told its to stop media helicopters in particular. Above 2500 is CTA so they would need a clearance then.
Surprised CASA can manage to do this...
I'd hazard a guess that the police and army have hotlines or automated procedures they can use for these restricted areas in an emergency.