The problem with Motorola stuff is that you need to either have a tech program them, or spend the money to get their software and programming setup.
HOWEVER, Ma Batwings allows free distribution of the programming software for orphaned radio series. This means that, depending on the FD setup, you MIGHT be able to get an Astro Saber (handie talkie) to listen in. The radios run in the $100 range. You will also need a RIB programming box, generics of these run under $35 and the adapter cable can be found for under $50. Thus, a complete setup (radio, battery, charger, RIB, cable and software) might be under $200. You can program any channel to not transmit, the radio will scan, and these are great units, even though they date back to the 1990s.