Australia's competition watchdog has given the go-ahead for NBN to take over the HFC networks currently operated by Optus and Telstra.
Late last year, NBN agreed to take over the existing Telstra and Optus HFC networks with the intention of making them part of the NBN.
The original agreements involved both carriers being paid to move their customers from HFC onto the NBN fibre to the premises (FTTP) or fixed wireless networks once those services were available in a particular area.
But following the current government's decision to adopt a multi-technology approach, the deals were renegotiated so that for the same price NBN would instead take over the HFC networks. The new deal with Telstra also included the copper network so it could be used in fibre to the node (FTTN) rollouts.
The idea is that using HFC and FTTN will allow NBN to cover more of the country, more quickly and more cheaply than the original FTTP and fixed wireless rollout.
The ACCC has now given draft approval for the integration of the Optus HFC network with the NBN, and the migration of Optus HFC customers to NBN.
This follows a similar decision last month regarding the Telstra copper and HFC networks and the company's customers.
According to Federal Minister for Communications Malcolm Turnbull, NBN's initial HFC services will be the same as for FTTP, with a maximum rate of 100/40Mbps.
NBN has already announced plans to upgrade its HFC network to the DOCSIS 3.1 standard, which has the potential to offer significantly higher speeds, including the 1000/400 tier that was announced in April 2013 but subsequently - and quietly - dropped.
The timing of the upgrade and the availability of faster services will depend on consumer demand, according to an NBN spokesperson.
Around 2 million premises are already served by the two HFC networks, and the plan includes connecting another 1 million premises that are passed but not actually hooked up, or pockets that aren't covered in areas that are generally served by HFC.
NBN intends to launch its HFC services in 2016 and complete the rollout by 2020.