If the FCC license is still valid the agency and personnel can still use those frequencies at any time. They may only use them for low-power parking control during the annual winter festival, or maybe they only use them at the police shooting range now, or for training purposes within the jail. Just because they were once the primary Dispatch channel doesn't mean they're no longer in use; all they could easily flip the switch back to using it fulltime as long as their license is current. Here in Indiana, we've had a statewide digital radio system for 20+ years, and I've noticed a lot of counties still renew their 'old' VHF frequencies. FCC licenses are valid for 10 years, so it could take decades before a county voluntarily gives up frequencies that are licensed to them. Many counties renew a license that has several frequencies on it because they still use 1 of them (likely a fire dispatch frequency for VHF pagers, or an interior jail frequency that isn't able to be received more than a city block away from the jail do to thick concrete and steel walls.); Again, if the license is valid they could use them for nearly any purpose at any time.
With that being said, I submitted a couple frequencies for depreciation a few weeks ago. The private ambulance service was replaced by an ambulance service from a large hospital network many years ago, that hospital network uses their own TRS for their ambulances along with the statewide TRS, the private ambulance service went out of business, and the private ambulance service's FCC licenses had expired several years ago.