Finally can a BA A320 captain join LH on the 787 as a captain?
Yes. Once you’re a captain in BA, you can be a captain on anything, provided you have the seniority.
My glittering career-path was: FO 744, Capt A320, Capt 787.
When I was a Training Copilot on the 744, I converted some 737 Captains onto the 747.
There were some restrictions when the A380 was introduced (some Airbus experience required).