It depends. I doubt it because the distribution needs to be considered. Replacing average drivers either an average system yields no benefit. If it's applied to both tails equally, then you haven't moved the average either, juar made it more homogeneous. You'd have to target the highest risk groups to make the impact. Many in those groups can't afford or won't adopt the tech - the elderly, low income (or less educated depending on the study), or young males mostly.
The better ways to target only the problematic tail is stricter testing, better education, and possibly permemant interlock devices for DUI offenders.
"How many accidents happen because an individual careful driver is, momentaritly, inanttentive?"
My guess would be probably about as often as autonomous systems screw up in novel environments.
That long tail of outlier clipping works on an individual human basis, too. How many accidents happen because an individual careful driver is, momentaritly, inanttentive?