I was pretty certain (and have confirmed by looking at the RRDB listings) that Washington County Law enforcement was encrypted. I was actually a little surprised to see that MSP is listed as being encrypted on the Washington County system but maybe I shouldn't be.
When St. Mary's switched to P25 several years ago, I believe all of their law enforcement including MSP went encrypted at that time as well.
Law enforcement to include MSP on the Frederick County system is still in the clear (for now) although recent discussions have indicated that Frederick City is encrypted.
Somerset County law uses Provoice. When FiRST went live down there, they had clear (nearly?) full time patches onto FiRST but have since encrypted those patches.
Surprisingly, Queen Anne, Talbot, and Caroline law for the most part stayed in the clear when the switched to FiRST recently. They like others wisely kept routine dispatches in the clear but have encrypted some tac talkgroups. Some operational data as well as personal information (like SSNs, etc.) needs to be protected. [side note: I recently heard a Maryland business using NXDN actually read out the entire set of a user's credit card information over their clear talkgroup - to include name, card number, expiration, zip code, security code on the back, etc. -- I was horrified but glad it wasn't my info!]
We'll know more when Wicomico and Worcester go P25 if they'll encrypt....I'm thinking it's a better than 50/50 possibility.
DC law is all encrypted.
Once a department or service goes encrypted, I really would not expect them to revert back.