Taiwan’s telecoms regulator plans to update its rules to allow the country’s mobile operators to share core networks, once they update their business plans and receive official approval.

The decision comes after the National Communications Commission (NCC) investigated Asia-Pacific Telecom (APT) for using Taiwan Mobile’s network to offer 4G service. The firms claimed to have a roaming agreement.

Chunghwa Telecom, Far EasTone Telecommunications and Taiwan Star Telecom had complained that APT, which has a 4G licence, was using Taiwan Mobile’s network and had not built its own 4G network.

The NCC ruled in February that APT was simply using Taiwan Mobile’s core network to offer 4G services, which is different from a typical roaming arrangement. It fined each company TWD300,000 ($9,700) for failing to report the agreement.

NCC last week fined APT another TWD300,000 for failing to fulfill its service commitments and for not applying for changes in its business plan.

The investigation helped the commission set the principles for how it would handle similar cases in the future, the Taipei Times reported.

An NCC representative told the Times that even though the commission has decided to allow 4G operators to share core networks, “this does not mean that one carrier can simply use another carrier’s network without building or using its own network at all”.

The representative said operators need to apply for changes in their business plans, which then need to be approved by the commission before they can share a network.