Don't know if this was the case but on my Pro96 I sometimes have the display show one TG but the audio is obviously from another talkgroup (since I recognize the dispatcher and unit numbers). I've seen this when one conversation ends but the radio apparently hangs on that frequency and passes audio from another TG. My 396T doesn't do this so I trust it more in cases like this.
Most D02 transmissions are in the clear. However, if you look at the RR data for D02, you will notice that the DCI may work out of D02 and their activities are encrypted. In that case so would their c-c traffic.