Responding to this article my experience is that Cathay Pacific does NOT auto-rebook passengers on cancelled flights.
I was stuck in September during typhoon Usagi in Los Angeles. My situation was exactly as in the article. I had a redemption ticket booked via British Airways on Cathay and needed to speak to BA to rebook my flights, and BA can only use award inventory space. I took whatever BA found and got re-routed through San Francisco a few days later. I wanted to get back to HKG sooner though, so I physically went to LAX airport to get the CX agent to rebook me on the next CX flight that was leaving LAX non-stop. It wasn’t really a problem although it did take a long time.
This also applies for passengers booked originally via CX. My friend had a paid ticket on CX in Premium Economy, same situation, had to wait at the airport and got a ‘verbal’ commitment that he’d be on the next flight. Wasn’t auto-rebooked and couldn’t reach CX over the phone. I didn’t trust his verbal commitment but he did get placed on the next flight out.
Surprisingly there were plenty of empty seats direct to HKG, since Cathay was booking connecting passengers on other airlines, which I thought was really great service for connecting passengers.
In summary I am a bit shocked that Cathay Pacific does not auto rebook passengers, even if the final destination is HKG. But they do try to help you if you are standing at the airport in person. My tip, go straight to the airport and speak to the airline in person, as they also control the seat inventory directly at the airport. I know it’s a pain to go to the airport, but if you want results when flying CX, that’s what you’ll need to do it seems.