My understanding is that MITM (but in a perfect way, using the leaked private key) is still required, if ephemeral Diffie-Hellman is involved. You can't just passively record the stream and decrypt it, since you don't know the exchanged DH secret.
The suggestion that the companies actually gave them the keys and this explains the "direct access" phrase makes a lot of sense!
However the private keys have to deployed, on scale. So if as someone here is suggesting the NSA has infiltrated those companies, they could have got those keys and just decrypt the stream.
I wouldn’t bet my money on that… but it’s more likely than breaking the encryption, and if they can get military secrets, I guess they could get the keys.
Also those companies could have just volunteered them—that’s where the emphasis on ‘direct’ access comes in.