I had a DUB-LHR-DFW-AUS award flight booked for later in December and was patting myself on the back for cleverly having a seat on the lone surviving AA flight out of LHR. Then last week BA cancelled the early flight out of DUB and the later flight arrives 5 minutes after the AA flight leaves. No proactive notice to me of course. There is still a later LHR-DFW on BA. When I called to switch to that, she said there was no miles availability but after I pushed she said she would submit a request to AA's liaison to BA to see if they would free up the space. It took about two days and they did free up the space, but AA said they would need to collect the additional $200+ in "taxes". The agent had no answer to "why isn't AA subject to those taxes" and I kicked and screamed but there was no budging so I forked it over. Otherwise there was no way to make that trip using AA miles without an overnight layover in LHR.

For the extra $ one gets BA's outstanding old style J seat and excellent Covid catering.