I don't know what it means, if marketed as "co-share" legs.
I flew a few times, with the booking from the Air Canada website, to KUL, SIN, visa Cathay Pacific, connecting HKG. But I found that I was never able to earn any AAdvantage points from those HKG-SIN or HKG-KUL flights with Cathay, and they were all business class tickets.