You need to speak to a NJ attorney rather than a NY attorney but in NY, the prosecution does not go forward with inoperable weapons. There are some prosecution offices that try to charge it as an attempt but it is not normally done.
The guns would have or be operable. The difference between NY and NJ is that in NY if the weapon is not operable no matter what there is no CPW charge. In NJ if the weapon, even if not operable, can readily be made to be operable there can be a charge of UPW. There is another difference between NY and NJ and that is in NY the weapon needed to have been loaded (loaded doesn't have to mean the ammunition was in the weapon just that it was readily accessible to the person in possession of the weapon) in NJ you can be charged even if the weapon is not loaded. I suggest your friend review the evidence with his lawyer and determine what the prosecution can or cannot prove.