It would sort of make sense, this shaking the tree method. They need Trump's team or others to make statements or leak information to justify searching for what they already know is there.
Similar to this:
http://www.reuters.com/article/us-dea-sod-idUSBRE97409R20130805
It's hard to say. Generally, the federal rules allow for discovery of all relevant material, even if inadmissible, as long as the discovery request is designed to lead to the discovery of admissible evidence. On the other hand, I don't know what, if any, different rules govern these kinds investigations. There's also the fact that this isn't a federal court, so it could be that otherwise inadmissible evidence (e.g. unlawfully obtained) would be admissible with which to publicly question Trump and his associates. But I don't know that that's true either.
These hearings strike me as more of a grand jury proceeding where a prosecutor presents all evidence, even wrongfully obtained evidence, and where the defendant isn't allowed to have their lawyer in the room. In a grand jury proceeding, about the only substantive right one retains is the 5th Amendment right against self-incrimination. I mention that only because we've seen public officials invoke that right in these types of proceedings. On the other hand, attorneys are allowed for those being questioned in these proceedings.
There's also the fact that this is a national security concern, which throws all kinds of rights out the window and in particular, allows the government to basically ignore the 4th Amendment (e.g. allowing the government to search and seize without a warrant---or even reasonable suspicion for that matter).
So, well... Fuck. I don't know.
