Telstra and Optus are joining the Australian Competition and Consumer Commission (ACCC) in a legal case initiated by Vodafone earlier this month over the draft decision not to declare wholesale domestic mobile roaming.
In May, the ACCC had shot down Vodafone's efforts to piggyback off Telstra's mobile infrastructure in regional and remote areas, where it has the least network coverage out of the three mobile providers.
The ACCC's draft decision [PDF] acknowledged that while incumbent operator Telstra has an advantage in regional areas, this alone is "not sufficient to justify declaration of a roaming service". The regulator also took Telstra's view that a declaration of wholesale mobile domestic roaming would result in less investment by Telstra in regional areas.
Vodafone subsequently filed judicial review proceedings, asking the Federal Court to look into the ACCC's "flawed" inquiry process on behalf of all Australian mobile customers.
"We know that many customers value coverage, and unless domestic roaming is declared, allowing all customers to access the infrastructure they paid for through taxes, too many will continue to be held prisoner to Telstra," a Vodafone spokesperson told ZDNet previously.
At a case management hearing in Federal Court on Friday morning, counsel representing Telstra told Justice Griffiths that the telco is seeking to become a party to the case as it will be impacted by the outcome, but is resisting any condition relating to costs that Vodafone is seeking to impose.
Counsel representing Optus said the second-largest mobile network provider in regional Australia is seeking to be admitted as an intervenor in the case on a cost-neutral basis.
Griffiths J said took the side of Telstra and Optus, saying it would be "inappropriate" to impose any cost-related condition, and agreed that Telstra should be made a party due to having a strong interest in the outcome.
The judge also imposed a limit on the length of the submissions to be provided by all parties to speed up the proceedings, with the ACCC's submissions to be capped at 15 pages, and Telstra's and Optus' submissions at 10 pages.
Counsel representing the ACCC said the commission is not able to estimate at this stage when the final decision will be made on wholesale mobile domestic roaming, as it still may need to consider previous submissions and seek further information, or it may receive additional submissions from participants prior to the hearing scheduled to take place on September 27 and 28.
"The commission will endeavour to give the parties and the intervenors as much notice as possible as to when it expects to make the final decision," the ACCC's counsel said.
A second case management hearing is set to take place on September 4.
Incoming mobile network provider TPG, the Competitive Carriers Coalition (CCC) made up of Australia's non-dominant telcos, virtual mobile service provider MNF, and mobile network provider Pivotel have also criticised the draft decision, arguing that it would lessen competition.
The Australian Communications Consumer Action Network (ACCAN) conversely said there is no evidence backing up Vodafone's claims that declaring roaming would increase competition.
Telstra's chief sustainability officer Tim O'Leary previously said there is nothing stopping Vodafone from investing in its own infrastructure in rural and regional Australia.
"Vodafone are not some sort of recent startup from NSW; they're in fact a very large multinational telco with $70 billion of revenue. Telstra has long been investing in rural and regional Australia. The amount of investment in rural and regional Australia from Telstra at the moment is probably unprecedented," O'Leary said at the ACCAN 2016 conference in Sydney in September last year.
Prior to the ACCC confirming its draft decision, Telstra CEO Andy Penn also said the telco will "immediately" move to expand its 4G network to 99 percent of the Australian population should the ACCC decide against wholesale domestic mobile roaming.
Optus also welcomed the ACCC's decision after backing Telstra up during debate on the issue last year, later announcing that it would similarly invest in improving its mobile coverage throughout Australia as a result of the decision.