Not sure where that was shot, but I am a supervisor for such an agency, and I have never heard of us destroying equipment removed from vehicles. I have a role in fleet management for my employees only, however have attended training and talked to people with a broader role in what happens to our fleet.
From what I know, local public safety agencies get first dibs on equipment, then Red Cross and similar disaster relief nonprofits, and finally the remnants are palletized and shrinkwrapped and sent to auction. The state sometimes obtains, for example, huge amounts of lights but only need parts of the systems, so the remaining items end up at the state surplus property office for public sale (with federal markings intact, in many cases).