Landline closure?
@pjmarsh - Great words, just to add that Openreach no longer allow ISP'S to order a PSTN service from them as of the 5th of September. That means that customers already on a PSTN phone line for now are safe but if they move ISP's or move house or their line is ceased in error, there is no way to get a PSTN phone line back.
They can take out FTTC/SOGEA but can't having a PSTN Phone service with it.
@Mustrum wrote:
@pvmb the BT Hub in the example has a phone adapter already built in - it would be easy enough for them to send it out with WiFi and ethernet switched off - so for them a low cost, low development cost solution. The little old lady in your example won't care as long as she follows the video and plugs her phone into the phone socket.
They may well have a simpler device, but from your original post you just wanted to find out what would happen, then you go off on a tangent - or tangents as more people try and help you understand.
Nope! You are wrong there, Mustrum. I have remained anchored to precisely the question I very carefully constructed in my OP. Sure, some people seem to have misunderstood my very carefully crafted question and gone "off at a tangent" asking me about my setup at home and referencing details about phone sockets etc. All of which is irrelevant to my original question. But that wasn't me.
OTOH some people (including yourself) have provided valuable insights - the overall result is that there IS still general doubt and some confusion over this matter. i.e. It ISN'T just me. 
As an adjacent matter: If I recall correctly, a few years ago, BT was reported to have paused the digital rollout because of questions such as "How do we make 999 calls if the mains power goes down?". That was supposed to allow BT to find a solution before continuing. They are going ahead now but I still haven't heard of any "solution". Indeed, reading other threads on this forum has shown the problem is not even as simple as was originally thought - the BT digital cabinets and even mobile phone base stations seem only to have limited battery backup.
For myself, I originally thought I would simply be plugging my DECT phone into my Plusnet Hub 2 router! Later I decided I would likely just let the landline go and depend on my elderly mobile phone, which is what I already use for most phone calls. However... the problem being the elderly base station I depend on, which is proving nowadays to be about as reliable as a 1950s Ford Prefect with a nylon stocking for a fan belt. I am not yet an 80 year old but am getting there. If the power goes off and the base station is also on the blink I certainly won't be able to call any emergency services if needed.
In the fullness of time it is not too fanciful to think there may be deaths. Then the newspapers will be full of headlines such as "Why weren't we told?", "How could BT let this OAP die alone at home?".
