The HKCAD does accept the FAA Comm and ATP for conversion. I am an FAA ATP holder and I am awaiting a course date with CX for a direct entry FO position based in the US. You will have to take a number of written tests when you go to HK for training.
If you are interested in Cathay Pacific as a SO, I would suggest applying now and then updating every 6 months. The first question I was asked in my first interview was "I see that you applied to CX in Dec 2004, why not sooner?". I think that they like to see persitance (sp?) and that you demonstrate that you really want to join Cathay.