Do you have a limit to the number of volunteers you have and do you do anything about maintaining recruitment. When I served as a volunteer firefighter in Germany, we had a similar issue due to lack of recruitment. We changed this by organising a junior firefighter scheme which started with kids aged 13 and went up to the age that they were old enough to join as a volunteer. Now they don't have the problem any6 more.
One thing we did was run total mutual aid with a nieghboring company. AA, CO alarms, MVC's everything. One thing you can do is have a duty crew. Put a sign up sheet with a 7-5 shift, give them Breakfast and lunch and see what happens. Cap it at 5 FF's. It might cost anywhere from $25 to $75 a day or less. Buy food and let them cook it. Do coffee and donuts for breakfast. We do it within a 3 company agreement at night and all companies reported having 2-3 crews instead of the one, at least until 12 or 1.
We set our our own preplans with our 911 system.Daytime calls other than routine med.calls get mutual aid right away.During the day we get 4-5 people on a good day so mutual aid is great.If you get there and the call either doesn't turn out to be what it's supposed to be or it's taken care of,the mutual aid can be canceled and returned.In our section of the country,we don't have any hydrants so its tanker shuttles.I'm a firm believer in getting the water on the road then if you don't need it you can send it home.Better to have it and not need it than need it and not have it right away.
Anything classed as an emergency (structure fire, wildfire in the summer, MVA with rescue etc) are automatic multiple station response and as both fire services in the State are on the same CAD, everyone gets the closest suport responded. Similar to other posts really.