We have a county mutual aid program that we try to have one dept host a joint drill for the other 3 departments juat something we do since our whole county is volunteer and the firemen, most of them, work out of town and need help to get enough people. So yes we do.
We just recently held a RIT class for the whole county, my dept. hosted and we had to take the skills back and teach the rest of our or their dept how to do it and we will be planning the class for the mutual aid soon.
We train together all the time. Being small rural departments both are lacking enough personnel to effectivly take on a major event alone so we have auto mutual aid. All our radio frequencies are the same. What one department doesn't have the other does. Works out quite well