I just got home from an award flight using Delta miles to Rome, connecting thru Paris.
We missed our flight from CDG to FCO because AF was late getting into Paris.
They did rebook us on the next flight out to FCO which happened to be on Alitalia in BE. But she must not have entered the right fare code on the new ticket, because when we got home both my wife and I got credit for the flight plus a 50% bonus posted to our Delta accounts.

So, it can happen but only on rare occasions and is always a mistake on someones part.

Also they lost our bags and we did not get them till noon the next in FCO.
Which is par for the course for AF from what I read here.
So I don't feel a bit guilty for getting the miles for the flight.