I find it hard to imagine that just hitting the brakes could trigger any such thing. Every weekend there's autocrosses and track events all around the country attended by supposedly around 500,000 people a year. Never in all my years of autocrossing and track events have I heard of anyone's car shutting itself off even from pounding over rough sections of track while in full ABS braking on R-compound (super sticky) tires. I'm not saying it isn't possible; after all the Prius has such high voltage that they may have made such a cutoff super sensitive, but it seems unlikely. The only hybrid I've ever seen autocross was an Insight, and he appeared to have no troubles.