It's referred to as "their internal network", but these taps were not within their buildings, as far as I recall. From my understanding, these are still leased lines run externally from facility to facility. It's been generally assumed that nobody is between points A and B on that line, but the line is still largely traveling through unsupervised space, and we are not the only government to have invested significant resources into tapping lines. (I believe both the US and Russia has submarines specifically designed to facilitate tapping undersea cables.)