Wikileaks doesn't do the investigating, at least it doesn't seem to me - they just make available the documents that are submitted if they feel it would be of value to the public. There is nothing to say that as a journalist, anyone else couldn't do the same with the documents of the WTBS. Especially if it is done with some informative or comparative analysis, everything should be public domain (except the private letters released to congregations).
Done correctly, I think the WT would have a hard fight on their hands.
DS