Nothing prevents any ISP from installing their equipment in cabinets except for the financial outlay and the fact there is no way you could ever build a viable business case. Prices for access are regulated by the Commerce Commission, but there mere outlay of a minimum of $20k - $30k worth of gear and ongoing monthly costs for backhaul to supply a handful of cutomers in every cabinet dosn't stack up. Even if you were somebody big like TelstraClear that might equate to 30 customers maximum from a cabinet which is just simply not viable.
+1 everything you said but on this part I dissent a bit
From memory the way backhaul cost is split between providers in a cabinet seems insane to me.
IIRC it's backhaul cost / number of providers, so in a two provider situation provider B pays 50% of the backhaul cost even if they don't have 50% of the customers, so you could have 10% of customers in a cabinet yet pay 50% of the backhaul cost!
Seems like a major disincentive for ISP's to get into sub loop unbundling, also the ComCOM Sub loop determinations took forever, came out years later that LLU meaning it was simply way too late.
Some ISP's, mostly in rural providers have taken up sub LLU and have gear in cabinets... probably only viable when they have near or over 50% of customers in a cabinet area.
I don't think the pricing is fair either, but it's a regulated offering set by the Commerce Commission. They set the pricing so others have to abide by it.
Many people think that regulation is great and the Commerce Commission always get things right. In many cases this doesn't happen, our regulated UBA offerings are all the proof you need for this. The Commerce Commission used flawed methdology in calculating retail minus wholesale pricing, and everybody has to suffer the consequences. DSL in NZ would IMHO be in a far better state if we weren't being held back by current regulation.