Bad outcomes are all but guaranteed when the NBNCo is expected to operate as a profitabe business and the captive ISPs have to buy capacity contracts. The ISPs have all the risk and can fail or pay dividends to their owners by judiciously managing their own problem.
It is in the ISPs interests to under-provision because their customers can only complain or move on hoping their next ISP will provide better service. A league table of how the ISPs deliver puts the onus on each end-customer, as usual to “shop carefully”, ie caveat emptor. A more reasonable approach would be to meter the ISP bandwidth and charge after the fact.
If the NBN backbone then got congested they could increase their capacity and that should be funded or at least guaranteed by government who is ultimately responsible for the white elephant.
Addenda, this thread is also relevant.
