Still seeing some untruths in there...Sheffield saying that MARCS doesn't work in 'the valley' (I assume they mean Black River metroparks). Well, if MARCS doesn't work there, the 5-city won't either. They are co-located, and if anything, Phase 2 has less range than Phase 1.
Plus 7/800 MHz doesn't get into valleys very well at all, where VHF will 'bend' over the rim of the valley to a fair degree.
Cleveland Metroparks had lots of problems with that in the past, and both MARCS and the Cleveland systems had to push to build sites that looked down into the valleys around the county better. (One of those sites is/was the Hopkins airport site. When it went down for repair a number of years ago, they were nearly off the air in the Rocky River/Fairview area. HQ had no service.)
"Interoperability" isn't what MARCS doesn't like. It's patches from other systems. It can cause...issues, especially if the other system locks up or has interference that then ties up a channel or channels on MARCS. It leaves issues that are out of the control of MARCS, but still interfere with it.
But they're slowly getting better at reporting this story...