You can now help buy congress's data

I understand this is fun activism, but I haven't seen a single "How" section on these things.

You have to give them your money to find out.

Isn't the only information legally available aggregate and non-identifiable?

I'd put "non-identifiable" in scare-quotes, but yes. This is a cute publicity stunt, but it won't work.

De-anonymizing datasets is generally possible to some degree, assuming the dataset has enough information value in the first place for someone to want it. (And it generally gets easier as more data becomes available with which to correlate.)

ISPs will never let this happen. These people scratched the ISPs back and the ISPs will scratch theirs. No way will they sell their data.

Our data will be up for grabs though if the ISPs choose to sell it.