#5, I'm not sure if you misunderstood me or if you are describing a situation where Customs is being avoided entirely both at CAN and HRB. By "precleared" I presume you mean cleared by Customs for release, not "autorouted" which is a baggage handling procedure to send the luggage onward without passenger involvement. I have never been on an international-to-domestic connection on CZ where one could avoid Customs. To clarify my previous post about a situation IF the bags are tagged to HRB:
1) Land at CAN. Go through Immigration with others. Go to domestic departures for flight CAN-HRB.
2) Land at HRB. Separation of passengers who originated internationally from passengers who originated at CAN. If bus gated, different buses will be use and international passengers get taken to international side of Bag Claim Hall for bag pickup and Customs exit, others taken to regular domestic side which has no Customs of course. If a jetway arrival, airline staff gathers up the international passengers and takes them to Intl Bag Claim.
If CZ only tags bags to CAN, then the pickup and going through Customs is done there and at HRB, bags are picked up on domestic belts. Either situation, I do not see how Chinese Customs can be circumvented.