I had figured that the treaty was in effect for the mojave BoS only, where are your F4 ideas?
Yeah the Mojave Brotherhood, I'm not entirely sure how that works though. So the Mojave BoS are not okay to shoot but the rest of the Brotherhood go ahead? If it is canon that the NCR and Mojave BoS made it treaty it was nothing but one of convience for both the over-stretched NCR and the morale broken Brotherhood. The Mojave Brotherhood are pretty bitter for the most part and the NCR is commanded by people like Moore, that treaty isn't going to last after the NCR stabilise Vegas.
As for the CWBoS? I reckon that Lyon's successor - his daughter - will probably secceed from the Brotherhood and form a new state with Rivet City.
In a dust-up between the two? Unfathomable. Right now the NCR still has weight of numbers and the local populace don't really have any pride - like say the Freesiders did which made them anti-NCR - the locals would probably support the proven stablilty of the NCR.