Just a follow with some more info after the duty manager called me this evening - He started off by insisting they were taxes, before relenting and saying they had to collect all taxes and carrier imposed surcharges for partners. They reserved the right to make schedule changes and the fact it was so far in advance gave them a different set of rules than if it were for tomorrow (say).

He also said the rules for award tickets and revenue tickets were different and award can only be protected on AA metal, whereas they were more prepared to deal with revenue protection on other airlines. If I wanted to stay on the BA flight, they would have to redeposit my miles (and taxes) and then book an award ticket on BA with the appropriate taxes and surcharges applied. He would even graciously waive the normal charge for that service.

So at the end of it he wouldn't budge. He also said my PNR is in limbo until they reach a satisfactory outcome for me or words to that effect. Which includes the original options I listed above.