NG military police rotate through Gitmo regularly. Kentucky, West Virginia, South Carolina, North Carolina, etc.
There are thousands of military and civilian contractors there that have nothing to do with the detention facility.
From the article, they are being sent in support of Joint Task Force Guantanamo:
"Approximately 150 members of the Minnesota National Guard will be deployed on Sunday to Naval Station Guantanamo Bay in support of Joint Task Force Guantanamo to provide base security".
Joint Task Force Guantanamo has everything to do with the detention facility:
"Joint Task Force Guantanamo (JTF-GTMO) is a U.S. military joint task force based at Guantanamo Bay Naval Base, Guantánamo Bay, Cuba on the southeastern end of the island. JTF-GTMO falls under US Southern Command. Since around 2002 the unit has operated the Guantanamo Bay detention camps Camp X-Ray and its successors Camp Delta, Camp V, and Camp Echo where there are detained prisoners captured in the war in Afghanistan after the September 11, 2001 attacks".