The county and ECI have a weird setup. The County 911 Center takes, handles and processes all emergency medical calls. There was a time that the County 911 Center would transfer emergency medical calls in EmergyCare jurisdiction to EmergyCare directly for them to process. However, with the County now processing those calls, they notify the EmergyCare dispatch center via radio. So essentially, it's a dispatch to dispatch talkgroup.
305 is a direct line for the 911 Center to notify the dispatchers at the EmergyCare communications center of a call in their jurisdiction.
306 is the talkgroup EmergyCare uses to communicate with their units, facilitate operations and dispatch their personnel to calls they received from the County on TG 305, etc...
The county does not dispatch for EmergyCare, they just notify them via radio of a call for service that one of the County calltakers took. EmergyCare dispatches and assigns their own units to the call and communicates directly with their units - the 911 Center does not.