All of these systems are controlled via wires. Wires are antennae. So, the wire going to your seat belt tensioner could end up conducting an electric current to the tensioner as a result of it picking up the energy from the radio waves being broadcast by a 2way radio. I'm not an engineer, but my father was. My explanation is about as simple as it gets. If you want more detail, you'll need to go to the library and take about a bunch of books by Tesla and Marconi.
Radiation can and does cause all kinds of problems with electronics. My buddy put some really expensive LED driving lights on his Taco and his FM radio has all kinds of static and noise from them when they are turned on. There must be some kind of transformer in the lights that is broadcasting radiation of the type that messes up his radio.