MMmmhrm,mmmruhuhammmm...lol......ehm...maybe but ulikely beacause before the storm begun,the NCR used the road from the divide as a trading route to and from california....but i understand your idea....anything could be.
It is entirely possible there could be some Legionnaires that were stranded when SHTF. After all, there was a catastrophe of sorts. NCR trade routes were apparently disrupted, but the Legion has a robust network of well-trained scouts even though they largely operate with brute force. In that sense Legionnaires can be rather desperate. I'm putting my money on the Legion being the only ones folly enough to still be navigating the route, but as you said it's anyone's guess.