Lets reasses the facts.
5) It was first built in 2000 so has been running for 12 years now, so their investment must be either paid off or close to it
6) Year on year SCCN has been reducing their cost of wholesale capacity, how many other companies do you know that have been doing that for the last 12 years?
So I'm not sure how a business case for another cable is impossible, given that they wouldn't even need to offer prices cheaper than SCC per se, they could just sell at the same per-mbps price, but in smaller blocks. Selling 10Gbps each to 10 companies costs no more than selling 100Gbps to one (ignoring the relatively small additional costs associated with dealing with more customers).
The main failure point of Pac Fibre is this:
SXC was paid off within 3 years. Except for operating costs, all charges we pay as kiwi consumers are basically profit.
PF would need to charge at a rate to pay back the investment within ~5 to ~10 years to satisfy investors while
SXC has already paid off their cable, and can lower their prices as much as they like and still be profiting.
If SXC wanted to, they could lower their prices to the point where PF couldnt compete and still pay off the cable over a expected lifetime of ~20 years.
SXC is going to need to replace their cable in the future, so of course there is a limit to how low they can go but in the mean time, I as an investor still cant see the business sense in investing in PF.