When I worked for the fire department, there were many instances and opportunities to interact with members of other municipal departments over the years.
For the most part, the encounters occurred day-to-day when working in the emergency response division. However, as my career shifted to the training center, I was assigned to the driver engineer instructor's position, and I was asked to get involved with presentations for different entities and other fire departments.
One day my wife started getting rid of some old T-shirts of mine (without me knowing) to give away to a local charity that resold used clothes. Many were fire department shirts that I had won from T-shirt bets during football season or other fire department shirts I had traded with our department shirts.