You can use ANY Amex to pay the taxes on a BA Amex 241 voucher, ignore what the rules say.
It is also worth knowing that Amex does NOT do name verification. You can even use an Amex belonging to someone else and it will still go through, even when BA puts your name in the ‘Cardholder’ box and doesn’t let you change it.
You will find that this MBNA move – together with the 35,000 mile sign-up deal on the AA card – is part of a game to position themselves for the retender of the BA credit card contract.
(PS Thanks for the plug Krug)