In days of old, when men were bold ..........
Seriously it depends. I used to work for Dan Air and the original 5 1-11s were from different sources. 2 were ex American Airlines (XCK & XCP) and had a Collins fit (618M-1) and needed Carbon mics. Two were ex British Eagle (TPJ & TPL) and had a Marconi fit (AD6400 if memory serves) and needed E.M mics the fifth was the infamous D-ANDY (ZED) and had the Collins fit too. So you see they were not non-standard just different radio fits. I imagine BEA being British would support British industry and have the Marconi fit.