Let's be clear about this, the data was not hijacked. It was routed either as part of a U.S based Chinese telecom company, or from a U.S owned telecom company to the Chinese (for what purpose I don't know, load balancing?).
What I'm saying is it was given to China freely, they have not hacked it from the U.S. I suspect this is why the own the master key, because they are either part of coallition of network providers, or the traffic in question was actually originating on a Chinese owned provider.