I can only imagine they've got an alternative plan. Given they had officials from Hungary secretly in parliament the other day it'll be a backdoor deal for a veto. Can only be found to have acted unlawfully if they're caught.
Now does it make it harder for the rebels to justify a VONC and national unity government?
I don't see how that could happen. The pledge from Johnson in the court includes a commitment that he will do nothing to undermine the Benn Act. Meeting with Hungary and securing an arrangement that leads them to exercise their right to a veto would obviously contravene that. Assuming that is the case, it would be clear to any observer that Hungary would only do that on the basis of some kind of quid pro quo with the UK government. If Johnson's plan is to get Hungary to exercise their right to veto an extension, surely the last thing he would do is commit himself in a court of law to precisely the opposite? He's got to have had enough of getting humiliated by the courts, and I cannot see how the result could be anything but that if this indeed were to be the case. Nevertheless, I concur that there's probably some sort of plan behind all this, but Hungary vetoing it does not seem to me a possibility anymore.