Only the enforcement units are encrypted. On occassion, though, you'll hear a unit calling Columbus and say 'secure' when they are actually in the clear. go figure. guess they can't tell the difference between secure & in the clear.
Pymatuning State Park on the Ohio side complains that they can't use MARCS that they have crappy coverage. Yet, they have a tower about 7 miles away. I have never had any issues picking up stuff on the site that would cover Pymatuning State Park. Go figure.