I doubt this is as big a deal as it seems.
Most if not all ATC off-site frequencies utilize dedicated phone line systems usually maintained by a local TELCO between the frequency site and the facility.
However, many are usually dug underground to avoid such things. That being said, we had one where an errant back-hoe operator dug and cut into one of the lines.
Losing a single frequency/frequency radar site is not quite as drastic as an entire Center losing power. Modern enroute centres use Mosaic'ing radar, which means the radar system processes multiple radar hits which overlap to provide a position, losing one radar site with frequencies shoud only cause a minimal amount of confusion/disruption, and very likely only a very small radar/frequency hole if any, especially in the United States.
It would take sometime to get everyone on another freq, and some radar targets may be lost for a short period of time, but unless two planes were on an imminent collision course it would likely go unnoticed to the end user aside from some frequency hunting on 121.5 and such.