Even with encryption the Simplex narrowband transmits would pretty much show up as a spike on any spectrum monitor equipment and with DF gear they can point out the location of transmits. I would figure that high end criminal enterprise would probably have a dedicated Countermeasures team with high end equipment to detect and triangulate transmits or determine if there is some kind of surveillance operation near by and if so they could probably then send someone with passive audio surveillance equipment to listen in.