Last month I participated in this exercise at YVR. That's me at the 20 second mark.

I was an "injured" passenger. Serious injuries.

After the "crash" it was 25 minutes before a first responder approached me.
Another 15 minutes before I was "moved" to the triage area.
55 minutes after the "crash" I was "airlifted" from the scene.

Fine print....the primary purpose of this exercise was communication between various agencies, about 30, not first aid, etc.

Even if you were one of the first transported from the scene, I suspect that would take a minimum of 20 minutes. Most would be longer. In a large scale crash with hundreds needing first aid, you'll be laying on the ramp a long time. I don't think there is more than a couple dozen ambulances within 15 minutes of YVR.

Fortunately the weather was nice. Beware, if one crashed at a warm location sun burn could be a possibility.