I've transited at PEK for 4 times so far. all booked with CA
HKG-PEK-FRA; FRA-PEK-HKG
HKG-PEK: Dragonair flight arranged by Air China, as the delay of the Air China flight was anticipated.
HKG-PEK-VIE-BCN; MAD-PEK-HKG
Again, I took a Dragonair flight for the segment HKG-PEK, as the Air China flight I booked was cancelled. The cancellation notification was made 4 days before my flight. Fought pretty hard for the Dragonair flight, citing my HKG-PEK-FRA experience.
Dragonair and Air China do have interline agreement, so my luggages were checked through.