Anon grew up in the area near Mt. Weather. Can confirm that the description of the facility is correct, based on other articles, historic facts, and people who have worked there.
No idea if the Delta Force story is true or not, obviously. The facility was created as a COG continuation of government, because of its hardened location and proximity to DC. It has storage facilities designed to protect national treasures in the even of nuclear war. I do NOT know the extent of FEMA activities there, although the article pretty much aligns with what you can read on Wiki.
Interesting observation: this facility was depicted in the series "The 100" about a dystopian earth. The decendents of the original Mt. Weather staff were still surviving in the bunker, conducting genetic experiements, and enjoying access to all the rich treasures that were stored there. Interesting story, and I found it curious.