Yes you can take CX LAX-HKG and then go by bus as well as an alternative to train. Be sure to have you CX ticket booked in minimum "H" class to get the AA miles.

Another alternative is you can book CX for LAX-HKG and then connect to CZ HKG-CAN. CX has provided many agencies with special fares HKG-mainland add on fares where if everything is booked under one ticket in conjuction with a CX transpacific, you can get the deal. You would have to contact local agencies to book this though. Remember the key is to purchase H, B, or Y if you are traveling in coach. Of course any revenue biz or first booking class will get you the mileages as well.