And is the language in cockpit one that the BEA head would understand? In an emergency situation would you revert to your language of birth, aviation English or a mixture. Surely as a professional investigator he would wait for a native speaker to interpret the language used and its idiosyncrasies.
IIRC with the Spanair Madrid accident - it took quite a while to come up with an accurate translation - despite much rubbish being talked on here when an audio file was released.