On HKG-PEK you can earn AA status miles/points on CX if the flight timings work for you.
Dragonair does give miles, but only on AsiaMiles (CX's programme). China Eastern flies HKG-PVG and also gives AsiaMiles.
HKG-CAN is best done by boat or rail if you are stopping in HKG. It's an incredibly short flight that really only makes sense if transiting through HKG. It is operated by CZ (China Southern) and KA (Dragonair) codeshares.