Ed,
Most (using term loosely) departments grab a MAC channel when they are calling for equipment from another agency. It helps keep everyone on the same page, instead of trying to coordinate traffic on everyone's dispatch channels. I ID'd MAC 7 digital when Tallmadge requested a MAC channel for this past weekend's CircleFest. Summit County had some deputies helping out, so Tallmadge PD, FD, and the SO all worked off a single channel.
MERC is used for major emergencies. The YRC fire last week used a MERC channel once the county HAZMAT was activated. That's when I found the updated MERC CALL and MERC 4.
MAC and MERC are a must to hear the big stuff.
Also, I've been hearing traffic on 42032. It sounds like school buses. It might be Akron going digital, as there are no known new subscribers on the system.