In and seen by NBN Co chief executive, Mike Quigley, wrote the broadband wholesaler would reveal the total capital expenditure required to build the fibre-to-the-home network.
Members of Parliament who agreed to the closed door briefing would also be told the initial intended pricing for NBN Co's wholesale offering to retail service providers.
"NBN Co's business plan projects that [wholesale] prices will be reduced over time," Quigley wrote in the letter.
While some of the knowledge expected to be revealed at the briefing this week is already in public knowledge - such as the $27 billion peak equity rate of the project - senators and MPs are likely to be told that the project could provide an internal rate of return higher than the current long-term government bond rate.
Despite continuing doubts over key points of the business plan - including the location of national points of interconnect and the pending heads of agreement with the Telstra - Quigley told senators Conroy and Wong that NBN Co could still reveal key points from the as-yet-unreleased business plan.
The Gillard Government has faced off increasing heat over its failure to release the business plan. Though original intentions were to make - the Labor government has since promised to release the entire 400-page report, but .
The closed door briefings have also attracted criticism, with the Greens and independent senator Nick Xenophon over confidentiality clauses which would prevent them from speaking about details for up to seven years. Family First senator, Steve Fielding, agreed to the briefing with a confidentiality clause of three years, but it is believed this has since changed to lift in December.
A spokesperson for Senator Conroy did not return calls at time of writing.