Optus has said it will build 500 new mobile sites and upgrade 1,800 sites to 4G as part of a AU$1 billion investment in its network over the next year.
Slated to be completed by the end of June 2018, Optus said it would use the cash for gaining spectrum in regional areas, and continuing its small cell deployments.
Optus CEO Allen Lew claimed the funding was the single largest investment in regional mobile infrastructure in Australia's history.
"Optus' funding is earmarked to expand coverage and improve overall network performance for residents, businesses, and our wholesale partners. It will also help build the network resilience that is critical to supporting public safety and emergency services during natural disasters," he said.
"Regional communities rely on a strong mobile network to support their key industries, and to deliver critical services like health care and education. Through this investment, Optus will help propel regional businesses into national and international markets by providing network reliability, high speed connectivity, and advanced technologies such as cloud and cybersecurity services that industries need to thrive and grow."
Speaking with journalists in Tamworth on Friday, Lew said the announcement showed the country did not need a domestic roaming declaration.
"Our position on mandated domestic mobile roaming has been that it will hold back investment, and we have made this investment to prove to Australia that, at the end of the day, competition will exist, and competition will exist without any mandated mobile roaming, and that we will do this to create competition and give choice to people," he said.
Deputy Prime Minister and local member for New England Barnaby Joyce hailed Optus' decision as "incredible" and said it had been accomplished without government assistance, even though 144 of the 500 new mobile sites fall under the auspices of the federal government's mobile blackspot program.
"It's going to make sure not only have you got the service, but you've got the competition in the marketplace to make sure you get the best price -- so you're not held over a barrel," Joyce said.
Optus said in May it would be parting with AU$1.5 billion to improve its network across Australia, following the ACCC's draft decision not to declare domestic roaming.
Besides today's announcement, Lew flagged at the time that the telco would be increasing the density of its metropolitan coverage.
Also in May, Telstra said it would similarly expand 4G to 99 percent of its network should the ACCC confirm its draft decision.
Vodafone is currently taking legal action to review the process under which the ACCC arrived at its draft decision.
Last month, Telstra and Optus joined the ACCC in its case against Vodafone.
A Productivity Commission report into telecommunications universal service obligation, released last year, showed that although Vodafone claims to have 96 percent of the Australian population covered by its network, only 7.5 percent of the continent's landmass is covered.
By contrast, Optus claims 98.5 percent population coverage and 15.6 percent of the nation's area covered, while Telstra said it has 99.3 percent of the population and more than 31 percent of the landmass covered by its mobile network.