Doubt it honestly...
HANS is great for a sudden forward STOP... It doesnt do much for side to side. Even HANS admits this. Thats not its design purpose.
This is my buddy...his passenger rear wheel broke and he ran it over and spun... he has a 6 point and a HANS, but no containment seat. This is a pretty benign incident... see how much lateral movement he has?
He now has a full containment seat.
A full containment seat with head restraint is likely what saved him.
FIA has some crazy data on head restraint seats. They are possibly as big a safety item as HANS, but for lateral body/head movement.
Its a huge reason I put a containment seat in my track car.
Racing seat with fiberglass shell, airtex material and upholstered customized on demand. HANS and HSC PATENT compatible and FIA approved.
www.ompracing.com
And that seat is small potato's compared to, im sure, what NASCAR is running with full up custom seats for each driver.