Ultimately it would have to go to arbitration to determine if the agreed acceptance criteria had been met. If of course no acceptance criteria were agreed on then the vendor has opened themselves up to a world of grief because the scenario you are painting will likely come to pass. A contract should always have agreed acceptance criteria but, of course, sometimes they don't and it's a horrific oversight.
TV2 Price at posting:
1.7¢ Sentiment: None Disclosure: Not Held