Has anyone ever worn the MP Brassard when conducting force protection duties?

um... yes... That is generally what MPs do.

Once upon a time, the Military Police Corps were issued metal LE badges, which were only authorized for wear on the Class A uniform. The MP brassard was used on the fatigue/BDU uniforms. Then the MP Corps got a new commanding general who promptly took back all the badges which have not been seen since (what happened to them?!). Now, with velcro patches, there exists a slap on MP emblem (don't know where you can get one if not assigned to a combat mission in the Middle East, etc.). There are some Korean knock-off versions of the badges, but are relatively poor quality. Bring back the original MP badges! Just my personal opinion...

Yes. At Ft. Meade, MD after 9-11 and for my whole 2003-2004 Iraq deployment.