Please cite which ITU standard and paragraph you believe that BT doesn't comply with.
So we are not talking about ITU standards at all then.
You have a complete choice of network terminals. You also have a complete choice of alternative VoIP providers.
I am not talking that deep down Digital Voice is a non-standard technology (albeit BT seems to be selling that as if it was best thing they invented since sliced bread) - they seem to be unwilling to open it up to be accessed using alternative hardware.
I don't think I have freedom of choice of the terminal since BT imposes SH2.
We are not talking here about changing ISPs either - about their compliance with law - _dura lex sed lex_
But that's a legal requirement and not the choice. If that's too much strain on the business model then copper lines should stay (and no - I am not a proponent of PSTN).
After all I didn't need to pay to get my Gigaset phone connected to BT network (or Doro or Panasonic or even Echo Connect device).
Please cite this legal requirement (for what I know not) that you keep plugging.
Do you seriously think that BT's lawyers would allow it to break the law?