The calls you stop getting
When the power goes out, the phones start ringing. Unless people already know.
Every affected customer hears about it, on any network
Tell an affected area what has happened and when it will be fixed, then tell them when it is. Connections to all Australian carriers mean it reaches people whoever their provider is.
Fewer calls asking what is going on
Every customer who received a notice is a customer who did not ring the contact centre to ask what was going on.
Send it from your systems
Trigger notifications straight from the operational system that already knows about the fault, through the API or by email.