NBN technician Rajav Kapil connecting an apartment block to the National Broadband Network (NBN) in Brunswick, Melbourne, Tuesday, March 11, 2014. (AAP Image/David Crosling)

The extent to which the government's decision to force NBN to switch to Malcolm Turnbull's Multi-Technology Mix model will expose it to financial disaster has become clearer this week from Telstra head Andy Penn's comments about his 5G rollout.

As Crikey reported in April, 5G is superior to NBN's mishmash of fibre-to-the-node and HFC cable, now being built at the direction of Malcolm Turnbull when the Coalition took power in 2013. It has previously been unclear what kind of impact 5G would have on this second-rate NBN. Now, Penn has provided some specific numbers on that, and it's deeply scary for NBN.