The September 18 outage, which lasted almost 14 hours, affected hundreds of triple-zero calls in four states and territories and has been linked to two deaths due to emergency calls failing.
A parliamentary inquiry into the incident will hold a public hearing in Canberra on Thursday.
Kerry Schott, who completed an independent review into the outage, will be the first person to give evidence.
The veteran executive handed down 21 recommendations after finding gaps in the telco's process, accountability, and escalation and information protocols.
The Optus board accepted all of the recommendations, agreeing to "move swiftly" to implement them.
Optus bosses, including chief executive Stephen Rue, are expected to outline what the telco has changed following the outage.
This includes technical work to ensure devices can access emergency services and an overhaul of personnel and culture.
Optus is a wholly owned subsidiary of the Singapore-based telecommunications group Singtel, which will also have a representative appearing at the inquiry.
The Telecommunications Industry Ombudsman says the number of mobile phone complaints about being cut off from triple zero has grown following the Optus outage.
Complaints to the ombudsman rose 3.6 per cent between October and December to more than 14,000.
More than 6000 of those involved mobile services.
Apple Australia and Google Australia will appear at the hearing, along with NSW Ambulance and the National Emergency Management Agency.
In a submission to the inquiry in November, Optus said it accepted accountability for its failures.
"As one of Australia's major telecommunications providers, we understand that maintaining uninterrupted access to emergency calls is fundamental to public safety and community confidence," the submission said.
The telco extended its "deepest sympathies" to the families and friends of the people who died.
"Optus apologises to them and to all those who sought help that day but could not access it," it said.
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