I understand what they are supposed to be, but how did Mike get his hands on them? And how does he know what he has are legit?
To go along with that, does he have anyway of proving these are legit captures? or is that what this is supposed to prove?
Simply described. Every communication whether it is data or voice has to establish a connection. The call request, the answer of that request, the answer back to establish the circuit, the circuit establishement, the actual transmission is all time stamped and recorded. It also has the volume of data transmitted during that period of time.
So once you have this data (from the network routers) you can discover every connection. You know when, how much, and from where it came and where it went.
Did that help?
Regarding where Mike got the data... as far as I know, that hasn't been disclosed yet.