It’s Openreach , not BT , that decide when and where FTTP is rolled out, BT have no more or less influence on that then any other ISP that uses Openreach infrastructure, like Sky , Talk Talk , Vodafone etc.
If a smallish area appears to have been missed out when the majority of the surrounding area has been provided with FTTP, the reason(s) could be these houses are simply on the wrong side of a PON boundary ( passive optical network ) each PON only covers a certain area /number of properties , so there will be neighbouring addresses that are just the wrong side of a boundary, and the PON those addresses will eventually be served by , hasn’t been built yet…or it could be there are specific problems that make a part of a PON area uneconomical to service so these are put on hold ( in the short term ) theses missed out areas will be revisited later in the program when funding is available, OR look to get the biggest bang for their buck , so the expensive to serve addresses can be put on the back burner and the focus is on the less expensive to build areas.
FYI , property built in the 1960’s through to the very early 1990’s often was served by buried armoured cables ( called DIG , direct-in ground ) , the lack of ducting or telegraph poles makes these areas very expensive to reengineer for FTTP , so often are missed out , if there are a mix of different age property’s , some built prior to 1960 , served by poles , they could get FTTP quickly, same as property built after 1990 as they are already ducted…DIG properties generally are left out of the program, or it could even be a number of properties have a blocked duct that may need considerable expense to fix , again they can be excluded on the grounds of being too expensive to service.
