On an amide, the BrO- is the nucleophile and the Br- gets attached to the Nitrogen which displaces a hydrogen from the Nitrogen. I am wondering why the Br- attaches to the Nitrogen and not to the carbonyl carbon.
Honestly I wouldn't worry about the mechanism. Just know that an Amide with a BrO or Br, OH- will give you a holfman rearrangement meaning you are geting rid of the carbonyl and forming a primary amine.
