It's also possible that the documents outlining the closest collaborations are too sensitive for Greenwald et al. to publish. Snowden may be speaking generally

It's also possible that the documents outlining the closest collaborations are too sensitive for Greenwald et al. to publish. Snowden may be speaking generally based off of background which he has seen firsthand, but indicated to the journalists that it should be kept secret. Hard to conjecture much farther without seeing everything. At this juncture, I'm going to continue assuming that the GCHQ equals the NSA.