The Australian Competition and Consumer Commission has given final approval for a $800 million deal between NBN Co and Optus.
"The ACCC has closely examined the information before it and considers that the likely public benefits and detriments of the [agreement] are finely balanced," it noted in its final decision (pdf).
The regulator went on to say the main public benefits of authorising the deal were "clear and quantifiable" and likely to be beneficial.
Final approval came less than two months after the watchdog conditionally approved the customer migration deal.
It paved the way for the gradual decommissioning of parts of Optus' hybrid fibre coaxial (HFC) cable network and the transfer of those customers onto NBN infrastructure.
NBN CEO Mike Quigley said securing an unconditional agreement over Optus was the "latest in a series of commercial, operational, policy and construction milestones that underpinned the progress of the NBN".
"The migration of Optus' cable customers supports the NBN's business case and confirms the network as the cornerstone of Australia's digital communications future," Quigley said.
"Today's final decision by the ACCC marks a further move towards a new industry structure in which open access to the NBN will allow any telecommunications and internet service provider the opportunity to offer a service to any customer via either fibre, fixed wireless or satellite."
However, final approval of the deal was not universally welcomed, with Deakin University's Professor of public policy, Michael Porter, calling it "a travesty of economics, undermining a competitive pro-investment strategy for broadband in Australia".
Porter said the decision was "short sighted and political".
"We need all assets allowing competition to be available, unless there is an overwhelming case the other way," he said.
"Rolling HFC clients over to the NBN early is not a priority nor a necessity."