Due to the nature of their business most companies use cell phones, Nextel, GPS, or some other secure system. Back when they did use radios all their stops and customer locations were coded. None of it made any sense. Example: "Truck 201 10-8 2702, 10-76 to 2355."
Most reputable security companies never use their client's names or locations over the air.
Brinks uses 467.8125 / 203.5 PL, a one-way, 2 watt transmitter, worn by the courier which engages as soon as they leave the truck allowing the driver to monitor their audio.