I really would hope that no situation is allowed to develop where there is a huge lot of waste with networks going in side by side overbuilding one another. We do really need some proper planning here. We don't need multiple ‘national grid’ type electricity systems running parallel to one another and the same is true for the internet.
Quite so, that is where the merits of “competition” fail. Networks will be paid for by customers, and multiple parallel networks will cost multiple times what a single network would cost.
Already around here, alternative fibre providers are springing up, causing roadworks and traffic chaos as they dig up the roads to lay their fibre. All of which cost will ultimately need to be recovered via customer billing. If BT ducts already exist, I’d like to think they could be compelled to strike a deal and buy space in these ducts, but I suspect no such common sense applies.