Your experience with the N. America BA RTW desk is par for the course. It can be incredibly frustrating to get them to price (accurately) xONEs originating outside N. America. That was the great thing about the BA IST office. You set the itinerary and got the PNR from the BA RTW desk, then sent the PNR to IST and they would send it to the rates desk and send you the price when properly computed, piece of cake.

With the IST CTO closed (and people evidently aren't making contact by email at all) one is at a loss as to who to write/phone to in Turkey to use this approach henceforth.

Maybe if AA is your first trans-oceanic carrier you could get the AA RTW desk to price it and arrange for pickup at the BA desk at IST. You'd need to get an itinerary that uses the AA/BA codeshare no. to LHR to connect to AA, avoiding the TK codeshares direct to JFK or ORD. Don't know if they will.

Sure wish AA would empower Tal Aviation (their IST GSA) to sell tickets on AA stock.