I have an answer(?) for this.
Stanford Heights has an in-house store-and-forward system that was built in the 1990s by a firefighter of the department. Prior to then, Niskayuna Police (who dispatched them and the other two fire departments in Niskayuna before 2014) and (to a lesser extent) Rotterdam Police would essentially send out tones that only triggered the siren, meaning that their firefighters would have to respond to the station to get information on the call unless they had a scanner with them.
I do not have the technical details, but the system is triggered by the Schenectady County tones. These tones automatically trigger the siren (if it’s not past a certain time since they’ve since shut it off at night) and start the recording process. About ten to thirty seconds later, the transmitter at the firehouse sends out the Colonie tones over their paging frequency and then plays back the message from Schenectady County. Colonie PD dispatchers can hear these, but since the system is automated, there is nothing they can do. This system has only had some slight changes since it was built. Because both Colonie and Schenectady County have retained their pre-trunk/digital paging channels on VHF/UHF, no major changes had to be made when Schenectady County went to a trunk radio system.
Stanford Heights is the only multi-county department in Schenectady County that does this. Pine Grove is dispatched by the UCC for all calls, including in the Guilderland part of their fire district, with Guilderland PD calling the UCC by phone first. Esperance is dispatched by Schoharie County for all calls, with the UCC calling Schoharie County by phone for any calls in the Duanesburg part of their fire protection district. Burtonsville is in the same boat, but with the UCC calling Montgomery County. Confusingly, until recently, whenever Burtonsville got a medical call in the Duanesburg part of their district, the UCC would have to make two phone calls: First to Montgomery County to send Burtonsville Fire first responders, and then to Schoharie County to send Esperance Fire Rescue Squad. Now, as of January, Duanesburg Volunteer Ambulance Corps serves the entire town, although Esperance and Burtonsville still do first response EMS for all calls in their respective districts, and Esperance still does BLS transport in Schoharie County.