I live in the middle of nowhere, and know several to many ways of driving back routes to anywhere I want to get if something would happen to block the main paved route.
But then all my vehicles are four wheel drive and I have the skills to navigate back terrain. In fact, I have even done a lot of back road exploration around Las Vegas, and some around Baker, CA.... I’ll have to check my topo maps to see if I can find back road routes.
So, I checked my maps... There is a county road (CR20909) that parallels I-15 Varying about 100 yards to 1/2 mile away from the freeway from Baker to Mountain Pass, and then there are more county roads from Mountain Pass on into Las Vegas, passable to regular vehicles.
I don’t know if there are any exits from the interstate to the county road, but surely there are places to cross the median and head back to Baker and access the county road from there, and head to Vegas if they really wanted to.
But then, the cops probably won’t let anyone do anything but stay penned up like sheep, much less actually organize a rerouting and guide people out of the trap..