I have just found out that BA can restrict viewing and booking capabilitiy on other CRS's based on their location, and even where the CRS is based on linked to.

BA uses Amadeus. But it has direct link capability to restrict sales to certain TAs using other CRS's even, like SABRE.

So even if your TA or expertflyer shows availability, the location where you want your BA flight booked will show ZERO space or when you try to book it, it will come back as a waitlist.

For example, if you booked your reservation in say BKK, your PNR will have BKK's computer footprint on it already. Even though the seat is available between say LHR and NYC, as your orignial booking started from BKK, BA might consider it low-yield and each time you pull up your booking and try to book the 'available' seat, your PNR will display waitlist status.

Ok.. what does this have to do with Oneworld? Well, it will impact on your booking capabilities from various sources, as well as restrict sales from places that BA might consider low yield.

Even for award inventory... I was once able to find seats through asiamiles on BA flight, whereas on BAEC could not find the availability. You'd think it would be the other way round !