Isn't it against FCC regs to intentionally cause cell phones to stop working? I remember some prisons wanted to buy cell jammers to prevent inmates from using smuggled phones, but it's illegal.
"Jamming" wireless transmissions does indeed run afoul of FCC regulation; but that's not what they did here.
They disabled the power to the base stations which were deployed in specific locations (locations which are not public property). I assume they argue that they are not under any obligation to provide access to these base stations. I also assume that the base stations in question are either owned by them, or provided by the telcos.
Technically, one of the wireless providers could probably raise a stink that this action made their service look bad, but I seriously doubt they are going to take a stand in this regard.
It's actually potentially more interesting than that.
AM/FM radio stations on licensed frequencies are required to be transmitting. Dead air has to be reported and justified to the FCC, or they can face fines.
I wonder if that sort of thing applies to CDMA/GSM radio towers and repeaters.