RichLond - I emailed AAdvantage with a specific list of flights and if they would qualify. One of them was the GB Airways flight to CAS. They said it would qualify.
If you look at one of the oneworld marketing brochures (usually available in the lounges), it shows a table with a column for each of the core carriers and which of their subsidiaries count as an equivalent carrier. Last time I checked GB Airways was listed for BA.