In Reprieve's eyes, BT was therefore partly responsible for deaths dealt from Djibouti drones, and should be answerable for it.
So I had a look at the OECD document that Reprieve are complaining BT are in breach of. One of the first things I see is
They provide non-binding principles and standards for responsible business conduct in a global context consistent with applicable laws and internationally recognised standards.
So, actually, the guidelines are completely irrelevant. What is relevant and what BT should be accountable for is any breach of applicable law.
Of course, if Reprieve win, it will effectively signal joint-supplier liability for any multinational from providing any products or services to any military or paramilitary organisation anywhere. Even in their home-base country. Which, frankly, ain't going to happen.
Oh, and, if BT can crack the encryption that the Yanks will have put on the carrier circuit, then they better not tell the NSA.