I’ve asked the official Association of German Banks to take a look into that matter because I wanted to be sure to have working IBAN when I hand it out to receive salaries or ebay payments on my Revolut.
They checked back with SWIFT who controls the IBAN registry.
They told me, that it IS possible to have two different country codes in IBAN and BIC. However, it depends whether Lithuana has defined an exception within the registry. But there is no BIC exception within the SWIFT registry for LT IBANs (they told me).
Thus, a bank, receiving a LT IBAN with a GB BIC can refuse to do the transfer. And that’s just because the IBAN is not compliant with the SWIFT registry. They CAN, but they don’t NEED to refuse it, though.
I also asked the German national bank to get their take on it, I particularly also asked about customers rights for such strange SEPA transfers. No answer here, yet. But probably, they’ll say the same. But if this is true, it has nothing to do with propagation of the BIC through the networks. The banks just are right if they want to refuse it, because their security system checks the IBAN with the registry at SWIFT and find a non-compliance because of a BIC registered in another country.
Of course, that’s just what they told me, nothing I know for sure. But they sounded pretty aware that this is not working that way Revolut wants it to work.
Hope this gets sorted out somehow.