Suit seeking relief that is parallel to an already-agreed settlement with a third party is not moot, as there is no proof in the record of present compliance, no guarantee of ongoing compliance, and the plaintiff wouldn't have standing to enforce the third-party agreement.
http://media.ca11.uscourts.gov/opinions/pub/files/201713170.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.