Seems to me that if they were attempting to cut off communications, they wouldn't snip a residential line, but rather take out a substation, switching station, or backbone. I know where I live in NY, the cable, telephone, and power companies occassionally use independant contractors to do work, who generally would not be wearing a uniform and may or may not have a vehicle with a logo on it. That was the situation when when the cable company laid the underground broadband line in my neighborhood.
The best way to put your mind to rest is to call the cable/phone/power company. If no one was doing work in the area, then they will report the incident to LEO and probably get more attention than you did.
The other possibility is that the guys were hot wiring the line for to obtain free cable and/or telephone.