Originally Posted by
ahks
Not true!
Based on numerous flights from HKG and ex-HKG, bags are tagged based on the fare class you purchased. So if you purchased Y, you will not get priority J tags nor lounge access, if upgraded to J at check-in. They usually will write "no lounge" on the boarding pass.
Different agents handle it differently (although I suspect that there's something written about benefits for op-up'd pax in the CX Passenger Handling Manual). I've had a friend who is GR and he got op-up'd at check-in and they still offered him a Lounge Invitation (I guess out of goodwill) - not sure about priority tags.