No department likes to put up with a shared frequency. Its just something the field officers have to mentally filter out, "not me". Departments use to help out by cross talking, talking on "their frequency" and listening on their scanner for a response from a next door neighbor departmnt. Once cell phones came in vogue, this seemed to fall away. Dispatchers sill use pt 2 pt. I do hear some officers say to their dispatcher, "I heard it on the scanner" or maybe the grapevine.