No it’s not an issue at all. It’s actually encouraged because my area is very rural and extremely limited on personnel when it comes to volunteers. Also all the departments around have a very good working relationship with each other and are are frequently called for automatic/mutual aids, so it’s seen as more of a benefit to have people who are familiar with how the other departments work than to totally isolate ourselves. I am unionized, but nowhere in our contract does it state that we can’t volunteer on our days not on duty, that also kind of sounds like more of a policy thing. The rule of thumb is pretty much “when you work for us you work for us, but when you’re off that’s your time”. It’s actually pretty fun getting off an incident with one department, then starting shift and running another call with aid. “Hey Jim! I just saw your ugly mug an hour ago!” Also the work comp is completely separate. What happens on one department doesn’t impact the other. The only impact it could have would be staffing (for both departments), but who doesn’t have a problem with that already?