Note Verizon *is* engaged in an aggressive campaign to migrate POTS users in FIOS-fed neighborhoods over. Their catch phrase is "Fiber is the only Fix." I was forced off two years ago.
The reason, as told to me by a recent ex-employee, is money. Not just their decaying, East Germany-ish, level of outside copper plant, but the
5ESS's feeding those POTS users. They may be a sunk cost, but they have {significant} ongoing license fees on their software aka "Generic".And as the number of POTS users declines, the $$/user goes up and up.
If/when you get VZ phone service over FIOS, which I call "FOPS", no 5E is needed. I was told all FIOS calls in the extended DC region go via a Ribbon/Genband switch in Reston VA. That's a lot of bits.
(Note there are two flavors of FOPS. One is regulated, tariffed, service. The other is from some {allegedly} arms-length VZ subsidiary called "Digital Voice" I believe. Or you can just buy data-only FIOS, and port your number to Callcentric or another VOIP carrier. That's the route I went.)
The unanswered question is what shall VZ do about neighborhoods lacking FIOS? In Maryland at least, they ARE required to provide service. Other states, they have escaped from that commitment.
We see they are deploying FIOS in some new areas, but I wonder how long before they start claiming 5-GeeWhiz cellular service, with VZ's cell-phone box screwed to your wall, shall be your only choice. I'm aware of someone in central Virginia already so served.