Some insight, for what its worth.
There has been some issues that have come up within the past 6-12 months regarding interoperability btween Ingham and Clinton Co. FDs.
1. The first issue was the general patch that was put into place by Clinton Co. on the 19P911 TG to their main PD Countywide dispatch. When I responded up to Bath Twp. on a mutual aid EMS call and contacted them on that TG, it created a lot of unwanted buzz and confusion. It turns out, they had our mutual aid TGs (TRICOMUT) in their system and we (the FD lay personnel) never knew it.
2. A HAZMAT training excersize was conducted at Looking Glass Fire Authority in the late fall, and it was realized that there was quite a delay in transmissions from their station (the site of the exercise) to the responding units. The quality of the radio traffic during the time that patch was set up (forgive me, I don't remember what TG we were on) was very poor.
Therefore, I do know they have been working fairly diligently to come up with a solution to this and many other problems that have persisted throughout the system. We now have a policy that states when we repond to Clinton Co. that we contact them on one of the TRICOMUT TGs, and we are in no way supposed to use 19P911. In the couple of weeks, it seems there has been a sudden increase in mutual aid calls into Clinton Co. I suspect the random nature of when Clinton Co. groups are heard or go active is only when they have mutual aid from Ingham Co. responding within their county. If I learn anything else I can share, I'll be sure to post.