That is main channel but all officers carry cellphones and in car computers now,they also have channels in the 800 range,that are not known,one officer mentioned it one time to switch over to 800.Pretty soon you will not hear them at all on conventional scanners they are going digital.
Sometimes they just forget to call it in. It happens. I used to work there and back then we only had 460.050 repeater for patrol and a simplex UHF for detectives. I think there is a secondary UHF repeated channel now. They haven't gotten on the P25 system. They may have been testing it at one time though.
Patrol officers were forbidden to have the detective channel or a second radio for North Alabama Net 155.010. Only supervisors and detectives had a VHF radio. It was weird, but we had Giles Co. TN and Decatur at least in our radios back then. Seems like some of the detectives may have had southern linc. They had installed a Linc base radio for mutual aid but no one really knew what to do with it then.