Since the subpoena was being sent to a 3rd party, not the White House, the accounting company could turn over the documents and there is nothing the White House can do about it, unless they can get a stay in place quickly. But if they didn’t have someone standing by at the Circuit Court with an appeal ready to file as soon as the decision was released, that would be legal malpractice.
As it happens, the Chief Judge of the DC Circuit Court of Appeals is none other than Merrick Garland.
Can a company be held in contempt of Congress? And who would they toss in a cell?