Well actually by the end of fallout tactics the Midwestern brotherhood makes their base in Vault 0 AKA Cheyenne Mountain, which is a real life instillation located in Colorado, here: http://i53.tinypic.com/34gu8o7.png and considering that the legion holds Southern Colorado I doubt it would be that impossible for them to have gotten their hands on a few suits of "mid-western" armor... (Even if only via killing and lotting a couple of Paladins).