I have worked in the Mountain states, but only in farm areas with irrigation, or on Indian Reservations.
I don't know much about these groups holding a "standoff" in the US West, but I remember the "white supremicist" farm that aided the OKC bomber was full of FBI and/or ATF informants, something that was sort of covered up in the news (but known to locals, which is why the second guy is still alive and in jail, despite a conviction in a state that is more death penalty happy than Texas: locals figure one of these days he'll tell the truth of who was behind it.)
Professor Podles relates the background on the latest self proclaimed militia kerfuffle in Oregon. He notes both sides of the dispute and then notes an earlier story about two robbers and potential bombers who eluded the FBI in a 1998 case.
he refers to one of the Hillerman Mysteries that also had a reference to the group: Hunting Badger.
One of the few of the series that I didn't bring with me, but it is on Scribd so I'll add it to my reading list.
as for the militia, this quote comes to mind: