I’m fairly confident that you are generalizing this a bit and that there are police and fire fighting departments on this planet that employ nurses. In general though, first responders who get injured end up in the same system than the people they save and need medical attention: hospitals. If you are in need of nurse aftercare, you are probably off on sick leave - so what would the nurse actually do? Especially in the smaller bf-nowhere operations, I don’t see how you could justify the cost. Plus, most firehouses have paramedics already. They’re not the same as a nurse but bring a lot of similar skills.