It'll be tough to win, because the bank was following a court order. You'd have to show the court did something illegal, e.g., was in on a conspiracy or something. And we know that courts won't throw their brethren under the bus.
Tokyo Rose was convicted of treason.
I'll confess to not looking at the case, but AFAIK, all the subpoenas were challenged, and a court allowed them. Banks could have moved before stay pending appeal.
Banks cough up accounts all the time, see national security letters, ex parte.