Just "learnt" a new restriction when making a multi-carrier award redemption.
Friend wanna to redeem HKG-(CX)-oMAD-(IB)-oEZE-(BA)-xLHR-(CX)-HKG
All sectors are shown available on CX/BAEC websites. When creating the booking, the agent insisted that the last segment LHR-HKG on CX flight cannot be ticketed as transit. Obviously he doesn't want to stopover in LHR and paying the outrageous UK APD. OTOH, the agent suggested to travel on BA aircraft in the last segment which the booking can be created.
From CX website, there is an interesting observation.
One-way LHR-HKG (CX and BA: Available)
One-way MAD-LHR-HKG (BA-CX: Available)
One-way EZE-LHR-HKG (BA-CX: CX flights showed as Unavail. BA-BA: Available)
Anyone heard/experienced something similar?