Digital Voice (or VoIP) is a fait accompli. I don't see any amount of lobbying slowing it down much, for a several reasons.
Firstly, It's essentially for BT to be able to replace copper connections with fibre to allow provision of Gigabit broadband. BT and other companies rolling out fibre will say the government is pushing them to provide fast internet connectivity. (I don't see that as a political issue Boris Johnson initiated Gigabit broadband projects, at one time aiming for all by 2025, and Corbyn was promising free fibre broadband, although with a more realistic date of 2030.)
https://www.gov.uk/government/news/work-begins-on-first-major-broadband-upgrade-under-5-billion-project-gigabit
https://labour.org.uk/press/british-broadband-labour-sets-out-mission-to-connect-communities-across-britain-by-delivering-free-full-fibre-broadband-for-all/
Secondly, the existing equipment the public switched network operates on is aging and will become difficult to maintain or impossible to replace - and some copper wire on the local loop was probably installed over 100 years ago (BT will make money recovering that copper and selling it). Hence, the network will become less reliable in a few years. (Granted VoIP on FTTC/VDSL circuits isn't likely to be that reliable. My Plusnet broadband is often interrupted; I hope that's caused by work installing fibre …).
Thirdly, keep in mind this conversion isn't just happening in the UK, it's happening world wide, so the market for PSTN/ISDN switches has shrunk - if not completely disappeared yet - and, in turn, so has their availability. Telcos like BT no longer make money out of PSTN now private individuals' voice calls can be made for free or very cheaply using WhatsApp, Skype, Zoom, various VoIP, or mobiles services, and most large businesses and probably many medium sized ones have already installed VoIP systems.
In my opinion any lobbying should focus on improving the installation of VoIP: providing battery backups where, assisting in liaising with care or other alarm providers where needed, being persuaded to support wired extensions to existing, multiple analogue phones, etc.
I saw a recent statement from BT where they described themselves as "the UK's largest provider of fixed-line broadband and mobile services in the UK" - no mention of 'phone' services. I'm not saying this is necessarily good, just indicating where realistic lobbying is likely to be effective.
Mr Google tells me a host of European countries such as the Netherlands, Estonia, and Germany have switched to IP phone networks, with Norway, Spain and Portugal not far behind. Further afield, Singapore has already switched off PSTN, with Japan and Australia targeting completion dates within the next 2-3 years. [1 Aug 2023]
https://www.yay.com/blog/voip/global-pstn-switchoff-learnings/#:~:text=A%20host%20of%20European%20countries,the%20next%202%2D3%20years.
And it's happening (or happened?) in the US too (only they called it POTS - the plain old telephone system):
https://www.comrex.com/news/the-great-switch-off-pots-isdn-shutdown-imminent-in-2022/
Michael Ixer ● 603d