
"Second parties" means the rest of the Five Eyes: the UK, Canada, Australia, and New Zealand. And while most of it is through the UK (likely involving this facility and their transatlantic cable taps at GCHQ Bude), all parties are involved. So, we now have an NSA document which says that the US is paying "our" GCSB (something both the GCSB and their spy minister have refused to answer). As for what they're getting for their money, the obvious conclusion is access to data tapped from cables in the Pacific.
So, "our" spies take foreign money to work for a foreign power. Isn't there a very ugly word for that?