It depends on what scanner/receiver you are using. Normally you do a band search in analog mode and it will stop on the control channel (or any other signal that is on the air at the time). You can tell a P25 control channel by the sound. After you find it you can analyze it to see what system it is.How do you spot p25 control channels?
I went through some of my recordings and most of the audio was ENC or was not decoded properly. I did catch this short clip of someone doing a radio check. Their reply was ENC.