score:2
Therefore the ECJ decided that Iberia Express, as operating carrier of the first leg of the journey, was potentially liable for compensation because ‘a right of compensation exists against the operating air carrier when a passenger fails to catch a directly connecting flight as a result of a relatively minor delay in arrival of the preceding flight, with the result that there is a delay in arrival at the final destination of three hours or more, even when the flights concerned are operated by different air carriers and the booking was made through a tour operator who carried out the booking of the entire flight journey via another contractual air carrier which did operate flights on any part of the journey.’
(emphasis mine)
So it's the operating carrier of the flight which caused the initial delay (which subsequently were amplified by missed connections) who is liable.
The decision is flightright GmbH v Iberia Express SA
Note that this is EU case law, it may or may not apply in the UK since Brexit. YMMV.
Upvote:6
As usual the law is poorly written in this regard. The law clearly specifies that the "operating carrier" is on the hook but it doesn't specifically cover the case of itineraries with multiplies airlines and how exactly to determine the "operating carrier" in this case. By almost all definitions the "operating carrier" in your case was British Airways, but the law isn't tight enough so there is a loophole.
The regulation does not explicitly address code-shares. However, the preamble states that the obligations created by the regulation “should rest with the operating air carrier who performs or intends to perform a flight, whether with owned aircraft, under dry or wet lease, or on any other basis.”
However, all of the examples I cite above are subject to caveats. First, the regulation does not specifically address code-share situations, and second, a code-sharing flight often presents the airlines involved with an opportunity to engage in circular finger-pointing, leaving the traveler stuck in the middle.
Full text of the law: https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:32004R0261:en:HTML
I would keep pestering BA and clearly state that they are the operating carrier. EVA was the "marketing carrier" for the cancelled flight. If that doesn't help, you can consider either file a complaint or engage a commercial EC 261 collector who will pursue the case for you but take a cut of the proceeds.