Lead shielded cables? I don't know that there is a solution to this other than requesting that people turn off their cell phones. Or, you could do a James Cameron and use a nail gun to tack everyone's cell phone to the wall. If there is a real solution to this, I'd love to hear it too.

Although it might look ridiculous - maybe wrapping most of the surface of the recording equipment in aluminum foil might help.

I feel your pain. What kind of camera(s) were they using? Onboard mics? Audio Interface? Cables?

I made the mistake ONCE of trying FRS headsets on a 3-camera shoot. I had a guy at the center (wide-shot) camera directing and running the video mixer while I did the audio. He was calling the shots to cameras 1 & 3, and everytime he keyed the mic, the radio gave off enough energy to glitch the video. (Thank goodness for redundant recording) So rather than leave the event with a nearly finished product I had to go back and edit around every video transition without losing continuity. - not fun.