The NY vending machine can not generate blocks on its own. It has way too little CPU power for that.  The vending machine can be as dishonest as it wants to as long as it is
CPU dwarfed by honest nodes. Actually, I wouldn't even call it dishonest. Someone paid for a candy bar. But it can not force the coin to go to itself.
The vending machine's average time to generate a block could be years. It would only have an hour or so before all honest nodes are working to incorporate the Mars vending
machine's transaction.