Keep reading if you want to know more... the information below is from the Australian government emergency alert website:
"Emergency services can send warning messages to mobile telephones based on the location of handsets as well as registered service addresses within a geographical area affected by an emergency.
Emergency Alert is the national telephone warning system used by emergency services to send voice messages to landlines and text messages to mobile phones within a defined area about likely or actual emergencies.
Emergency Alert is just one way of warning communities and will not be used in all circumstances. Emergency Alert relies on telecommunications networks to send messages, and message delivery cannot be guaranteed".
For more information you can visit Emegency Alert FAQ link FAQ for emergency alert
Watch a Youtube video via Emergency Alert Australia video
Source available: http://www.emergencyalert.gov.au/
Issue date: 25/09/2016