As far as I know the data in your profile creates another profile on Amadeus (the GDS BA is using). Whenever a booking is started and your BAEC number added all the information that is stored in your profile is automatically added to your reservation (e.g. passport number, dob etc) - and a seat allocation is made immediately (except for the case when a seat assigment is not possible or allowed). All that information can later be seen when you retreive your booking on Ba.com "Manage my booking" - it is just mirrowing the data in the Amadeus booking.