How would the time scale of a different company doing some other issue be of any use.
If BT and it is only an if, do decide to do it they will do it on their timescale that suits their business model and not that of some other company.
To give you piece of mind you could always pick a date and work towards that and if BT issue a shorter date you just speed up whatever you are trying to achieve if you have not already completed your task or if BT pick a date further away you can adjust your process accordingly.
