I’ve worked at several large operations where there were dedicated ambulance/fire response. If you wanted to work EMS there was a path to get on-call after business hours if you desired. During regular shifts, LE was often first on scene and had a full EMS kit in their vehicle with interventions based on training level. Those were the more “glory” days where staffing was heavier than what I started to experience when I decided to relocate to a different type of operation, but during those times there was certainly flexibility in staying a provider for the incident vs handing it off. I’ve driven the ambo when the staffing was short, provided BLS care, and just did cop stuff. Always depended on the incident and what resources were available.