Yes, you can hear them by open scanning. It's not like listening to a channel, though. It's more like a two way phone call. Each radio has its own ID and they can call each other. When it shows up in the scanner, it's a longer number than the usual TG ID. If you hear someone talking and can figure out who they are, you can save their ID and put a name with it in the scanner. That way, you'll know who it is in the future. Pretty cool.
Here are a few I have. I didn't save the PD because I didn't know who they were...
AC 2 (Asst Chief Nathan) 753338
Communications Chief 753430
Training Chief 753258
EMS-3 (QA/QI Manager) 753272
Battalion 1 753336
Engine 15 I-Call 753415
Rescue 16 I-Call 753421