Fair point
as far as it goes.
But it shouldn't be that they are ALLOWED to access the openreach ducting - they should be REQUIRED to access the BT ducting on demand. i.e. they MUST provide 100% UK-wide coverage. If anyone asks for an e.g. Virgin provided cable in Auchtermuchty (though $deity knows why anyone would) then they MUST provide it at no more than the price charged by BT.
Fair's fair, we don't want them cherry-picking the cheap and easy places like the postal companies. If they want to break up a monopoly they must provide at least the same service at the same price.