Uniden's "Close Call" feature as well as Whistler's "Spectrum Sweeper" should be able to catch them if they're still conventional analog. Unless they moved to some form of digital/encrypted gear these days.
Don't think they were encrypted, but was definitely a DMR/MotoTRBO trunked system. We were issued XPR-7550s, had a few open mic issues that were resolved by inhibiting the specific radio.