Based on their sites, I believe they're UK-based company (and US endpoints are just endpoints, in case someone wants to have US-located exit to access US-only services), so it makes somehow reasonably harder (but not impossible) to correlate between the client and their traffic.
Still, I don't see any significant difference between NSA and GHCQ, except that we have (thanks to Snowden) some details of former's operations leaked, but the latter's remain secret (or I didn't pay enough attention to the news, maybe).
