The only "rival" Verizon has is AT&T and AT&T needs those tiny pockets of Verizon country to "prove" that they are functioning in a competitive environment and not functioning as a monopoly that needs greater regulation. The same goes for Connecticut where the former SNET territory is now owned by AT&T and resides in the middle of Verizon country.
The fiber network is highly meshed. This sabotage was done by people who knew the physical topology of AT&T's fiber network and knew that they could isolate a geographical area by cutting the fiber at Blossom Hill and Monterrey in San Jose and on Old County Road in San Carlos. This is not obvious to someone who doesn't know what lives down man holes and what the CLLI codes of the hardware is.
I live in the area affected. We lost all 911 access. NETCOM was reduced to radio communication and residents were told to drive to the nearest sheriff’s office, substation or hospital in case of an emergency. Could be a labor action or it could be an exercise testing how to shut down emergency communication in a fairly large area. Kinda like the first World Trade Center bombing testing just what it would take to successfully accomplish the deed.