NBN Co's revised draft corporate plan, given to the Australian government last year, originally contained a proposal for fibre to the basement, but it was removed in the publicly released document in August 2012.
Under the current government policy, NBN Co is rolling out fibre to 93 percent of Australian premises, including multi-dwelling units (MDUs) such as apartments and town houses, despite the added complexity of replacing in-building copper with fibre.
NBN Co CEO Mike Quigley confirmed in April to the joint parliamentary committee investigating the National Broadband Network (NBN) rollout that the company had assessed switching to a fibre-to-the-basement model, which would have been more cost effective.
"From time to time, the company looks at ways of doing things perhaps more cost effectively in line with what we think the government policy is, and we may put those options before the government," he said.
"Obviously, we looked at the option of running fibre into the basement, putting a small DSLAM into the basement, and then using the existing copper. That has certain attractions, obviously, as you do not get into structural separation issues because normally, that copper is owned by the building owner.
"There is no question there is a saving to be had by not having to fibre a multi-dwelling unit, but there are some other issues that need to be dealt with, such as how you ensure that you get analogue voice, which is a tricky issue."
At the time, Shadow Communications Minister Malcolm Turnbull said that NBN Co executives were interested in looking at more cost-effective policies, but were bound by strict government policy. He has indicated that his own NBN policy would see fibre rolled into the basement for apartment blocks.
ZDNet filed a Freedom of Information request with NBN Co in May, seeking access to the MDU study conducted by NBN Co. Last week, NBN Co refused to release the document.
In the decision, NBN Co said that the MDU study was an appendix to the draft revised corporate plan, which was submitted to the Cabinet last year.
On advice from the Department of Prime Minister and Cabinet (DPMC), NBN Co has rejected previous FOI requests for the draft corporate plan, and again, on advice from DPMC, rejected ZDNet's request on the grounds that it would reveal Cabinet deliberations.
ZDNet has requested the Information Commissioner to review this decision.
Neither Turnbull nor Communications Minister Stephen Conroy had responded to requests for comment at the time of writing.
NBN Co has a history of refusing access to documents under FOI, including access to the full AU$11 billion Telstra deal, the draft corporate plan, and documents outlining why Chinese network giant Huawei was banned from tendering for the NBN.