... The ‘Emergency Alert’ system currently sends warnings by recorded voice and text message to landlines and mobile phones based on an owner’s billing address rather than the actual location of a handset at the time of a disaster or emergency.
This has meant that people caught in a disaster zone, who have a billing address outside the affected area, have been unable to receive the vital and potentially lifesaving warnings.
Following the Interim Report of the Victorian Bushfire Royal Commission in August 2009, the Australian Government supported the Commission’s recommendation to implement a national warning system based on the location, in addition to the billing address, of a mobile phone. ...
From: Funding for location based emergency warnings, Joint Media Release, Prime Minister Julia Gillard, Attorney-General Robert McClelland, Australian Government, 14 September 2010In a disaster, such as a bushfire, the political level of government effectively ceases to function, with control being transferred to an emergency controller.
In the ACT the controllers is normally a police officer (ACT EMERGENCY MANAGEMENT ACT 1999 - SECT 22). The chief minister just has to make the declaration in "writing" (Section 20), then have it broadcast by a television or radio station and published in the Gazette some time later (Section 21). The Chief minister could issue the declaration from their mobile phone and have it sent out via the Emergency Alert system.