Currently the BT rolloiut is running heavilly behind schedule. If we take the lastest schedule there are a 172 exchanges listed as due for completion by the 30th September. Assuming 79 working days in that quarter it means they have to average 2.2 exchanges a day. To date they have averaged 0.6.
Don't worry about it, people will I'm sure jump in and tell you that it's fine and to go easy on BT if they haven't already.
As you rightly point out though these are BT's dates and if they can't keep to them they shouldn't have supplied them, simple as that.
For the poster who mentioned that they didn't have to do this, yes they did. They were years behind most of their peers in starting an NGA rollout and are playing catch up to compete with Virgin, their catch up being a relatively modest almost universal FTTC with FTTP rather cleverly supplied 'on demand' rather than to dense urban areas as their peers may have done.
BT are late to the game and have made huge amounts of noise, doesn't change that their coverage is spotty, their claim of coverage is quite carefully framed as covering exchanges that pass a certain amount of premises rather than the actual amount of premises that can take the FTTC service, and they've cunningly avoided having to spend their own money on FTTP for the most part by offering it on demand in 2013.