It's 50/50. Probably less. In general, don't expect fsd to avoid crashing, it will likely do something to make the crash less severe, but still crash.
Here are some stories from my NoA experience. With my radar tesla I was merging onto the interstate, in my blind spot after the merge was a drunk driver unbeknownst to me. NoA was on and then I felt my car hard swerve. I panicked but didn't disengage, I looked in my mirror and saw the drunk driver pushing into my lane, trying to pit maneuver me and my tesla dodging it. Without NoA, i would have had at least a damaged tail light if not worse.
I was driving my radar tesla to pick up some food at twilight, I was looking up at the clouds on a relatively empty highway while on NoA (I know, shouldn't be cloud gazing) and a tire was in the road. I didn't see it but my tesla began beeping with the red wheel to take control immediately, which prompted me to see the tire and manually dodge it by a few inches. I'm not sure if the beep was because of NoA or a very lucky wheel nag was missed.
Driving home one weekend on NoA on my fsdb tesla. I wanted to do a automatic lane change to put NoA in the faster lane. Checked if clear and hit the turn signal button. Tesla began going to the left lane slowly then suddenly, violently turned back into the right lane. It was so rough my brain registered it as a crash, I saw a bmw blasting past going 150 mph. I wasn't looking that far back for problem drivers when I was checking the lane if it were clear.
But like I said, don't expect it to save you. Some negative experiences to temper your expectations. When I first got my radar tesla, I tried letting it do automatic lane changes without my confirmation. Unlike last time, I saw a speeder in my left mirror, it didn't care and tried changing lanes, putting my traffic following(slow relative to him) car in front of him. I disengaged pulling my car back into the original lane. If I hadn't, the speeder definitely would have hit me. I haven't let NoA do unconfirmed lane changes sense.
There was a deer in the middle of the road it didn't see one time, I did.
Dumb summon stopped responding to stop commands and ran into a curb one time, causing 600 dollars of damage. Remember you can emergency cancel with a door handle press.
Smart summon tried to crash my car twice. Luckily stop commands from the app worked, I don't smart summon anymore.