See this is where I think having a professional experienced fire fighter involved might help. Paid or not, the benefit is at least potentially there for the community.
And how is working 6 hours part time as a firefighter anymore tiring than working 6 hours dry walling (or whatever) in your off hours anyway? I mean, really? That seems to be the point of contention that the union is floating anyway.
Fires aren't scheduled. I've gotten off work at five, been called to a fire at six and been out most of the night til 5am. My employer does not expect me to come to work in that situation. This decision by the union is all about protecting the union but without knowing the details of moonlighting rules for the city it's hard to get into specifics.