It's been a while, but years ago I believe AMR was primarily heard when dispatched for Kent and Ottawa County(Holland). As you got out of the metro area and into surrounding counties then other ambulance providers were used as well like Wayland and Rockford, etc..
In the DB there is no listing of a Freq for AMR, no tag either. For the counties etc on MPSCS, is all of the ambulance traffic now on P25 or just patched or ??
I asked a question a couple of months ago about the EMS med channels as they seem very quiet now. I was told that they are on MPSCS, this I cannot confirm since I don't have a MPSCS capable radio. It appears there are different TGID's on the Barry system for ambulance radio traffic as well.
Also, I could only find 1 hit of AMR in the RadioDB, maybe they decided to go on to MPSCS.