The former CEO of Australia's NBN Co, the entity responsible for building and operating Australia's national broadband network (NBN), Mike Quigley, has hit back at two years of being blamed by two prime ministers for the troubles that beset the project's multi-technology mix model (MTM) mandated in 2013.

In particular, Quigley says it's no longer reasonable to blame either costs nor the 2020 completion date for the fibre-plus-copper-plus-cable on either the former fibre-to-the-premises (FTTP) plan or the previous management team.

Of cost blowouts, Quigley told the Australian Broadcasting Corporation's Background Briefing programme, it's clear that the MTM mandate introduced by former communications minister (now Prime Minister) Malcolm Turnbull is behind the worsening cost position of the network (which, instead of the sub-AU$30 billion price tag promised before the 2013 election are now forecast to fall between $46 billion and $56 billion).

“What you can demonstrate on the NBN Co's own numbers … you can absolutely prove that the $15 billion has nothing to do with the fibre-to-the-premise (FTTP), or the fixed wireless, or the satellite – the original technologies.”

Quigley told the program that the FTTP costs “came down between the strategic review and the latest corporate plan, which means the actual costs of the other parts, the newer MTM parts, have gone up more than $15 billion.”

“We had four years of being audited by a number of organisations”, he said. Those audit reports – which included assessments both the Australian National Audit Office and PricewaterhouseCoopers – are “absolutely valid”.

Under the new model, he noted, nbn TM has also had to assume costs and responsibilities that under the old plan remained with Telstra.

Under the FTTP rollout plan, Telstra was responsible for its infrastructure until the fibre was in place, after which the copper would be decommissioned. Under the MTM NBN Co, now called nbn TM , has an ongoing responsibility for the fibre assets.

Quigley also said the costs of integrating two new technologies (FTTN and HFC) into the NBN's IT systems is expensive.

It's regrettable, Quigley told the programme, that this particular omelette can't be unscrambled: the Telstra agreements in place and nbn TM 's ownership of the copper assets make it impossible to return to FTTP.

Since the commentary on Quigley's legacy has been all in one direction so far, The Register expects the prime minister will mount a spirited response before too long. ®