You can also see Radio IDs and know it is being used by a particular group of people or agency, you can also use the encryption AlgID/KeyID to identify users and positions. For example I know the RID range of our local police, and I know the KeyID for patrol encryption and detective encryption, so I can put two and two together and it is usually four.
I had put a Google alert so that I would get emailed anytime the news talked about an upcoming SWAT training in my city. Then I would watch the radio on those days and eventually I was able to figure out what encrypted talk group they were on. 🧐
Radio IDs aren't encrypted, only the voice traffic, depending on your scanner or SDR software you are using they will decode just fine. Here is a photo of the screen of my TRX 1 scanner it shows the Radio ID and the E for encryption.