Supposedly the car rides up over the subframe so the engine goes under the floor and the steering wheel pulls away from the driver.
Unfortunately in practice all sorts of weird things can happen, I've seen tests that some crumplezones don't do what they're supposed to in real accident situations and are really dangerous.
It's just that the regulation tests don't cover all types of real world accident. One of my favourites I saw involved driving a car head on into a concrete block at about 15 mph without the brakes on. In a real accident the whole attitude of the car is different as the brakes are generally hard on so the nose of the car is down.
In the case of the mini this means that often the front
edge of the subframe passes under the other vehicle so the engine takes the
impact, this simply tears off it's mountings and heads for the occupants. I have
seen a pickup that had a head on with the clocks pushed out of the way by the
cylinder head, scary.