We rarely use phone lines to monitor fire panels anymore. POTS lines are hard to find and the digital lines voltage varies too much to work well with Panels looking for �x� amount of volts.
Cellular dialers and IP are replacing the old phone lines pretty quickly.

The company that owns them might change, but they have a purpose. However, owning and maintaining them is expensive and with declining revenue I would expect companies to continue to sell them.

edit: Dumb question..........How easy is it to knock out cell service vs. landlines in a ww3 type scenario?

Copper,, POTS, Outside Plant, Twisted Pair, etc is going out. Too expensive given the cost too maintain vs what they are getting in return. When I worked in the NE a few years back people wanted off if it but there were no alternatives. 5G and combo fiber is where it is at.

They will still offer the VOIP or cell based lines and gradually phase out the landlines. This has been going on for a few years now already. I retired from SBC/ATT in 2013 and it had already started with the residential lines.

When I left SBC/ATT in 2013 they were already transitioning residential lines to a cell based line. These were in the copper only areas that didn't have decent broadband capabilities. In other areas they were pushing VOIP lines with the broadband service.

NFPA 72 changed in 2016 to allow the use of cellular, IP and 2 way radio as primary communications for fire alarm.

All phone lines will be digital only by 2023, no more P.O.T.S (plain old telephone service)

Most of the Municipalities around DFW are requiring the above mentioned communication methods for fire alarm. I have had several customer tell me that one phone company has started to charge them $1,800.00 a month for P.O.T.S. service per line to get them off the system early.

If they continue to offer data/voice lines with e&m signaling, we can use that instead of copper pairs. BUT, there are millions of copper pairs at residences that ATT will have to convert first.