The report found a key cause of the outage was a problem with Optus’s 3G network.

During the outage, Optus’s 4G and 5G towers shut down, meaning emergency calls were diverted to other network’s towers — known as camping on.

But the network’s 3G base towers did not shut down, so those calls got lost along the way.

“Some devices … attempted to make emergency calls via those [3G] towers (rather than look to camp on to another network), even though no mobile service was being supplied by the Optus network,” the report said.

…

The recommendations include:

• Obligate telcos to shut down their towers during outages, allowing triple-0 calls to be carried by other networks
• Establish a “Triple Zero custodian” whose sole responsible is to make sure the system is working
• Force telcos to share real-time information about outages with emergency services organisations and authorities
• Force telcos to file a timely post-mortem on major outages to the regulator and the government — including what caused it and steps being taken to resolve it, with a clear and detailed timeline
• Review the government’s contract with Telstra to run the triple-0 system, with any changes to be made within a year
• Introduce an industry-wide approach to responding to consumers affected by large-scale outages
• Establish an agreement between telcos requiring them to help each to manage and resolve outages
• Review all legislation and regulation relating to triple-0