From ISP review.
After a bit of digging we’ve managed to learn that ownership of the joint venture does indeed split three ways, with Sky and TalkTalk both putting £5 million into the roll-out (CityFibre’s contribution is through their existing network / assets). Apparently none of BTOpenreach’s infrastructure will be used (i.e. no use of their cable ducts via PIA). The new network will thus remain entirely separate, with micro-trenching being part of the process to help build it.