They refuse to pay for a HA service
The Governments in Australia, like many organisations, refuse to pay top dollar for a highly available mobile network so their argument fails.
it would be cheaper for them to request special access rights under an emergency using APNs etc for Emergency services in a particular area when needed. Communications during the normal business day is easily accommodated by current commercial offerings. However if you ask them to pay a premium for this service they so no and go for the cheapest offering from carriers.