It depends on the structure of the bargaining units. If all the workers at the casinos in question belong to the same local or have the same contract (which I believe they do), then votes are not tallied by individual casino, so no one will know if one casino employee group is for or against the contract. All would be bound by the overall contract vote.

On the other hand, most "management" entities which are subject to the same contract band together into an Association for bargaining purposes and all agree to be bound by the results of the negotiations. Occasionally an individual Company will break the agreement and settle seperately. Hope that answers your question.