Originally Posted by Airprox

You assume incorrectly, departing and arriving pax are segregated. You will have to make your way to T1. If you are hand baggage only or you are on one booking and BA has checked your luggage through to QR then you can go through transfer security in T2A where you arrive and then take the airside bus to T1. If your luggage is not checked through then you will need to exit T2A, collect your bags and then make your way to T1 via the CDGVAL train or the landside bus.