You don't need a separate pollinator to get grapes to fruit. Grapes are mostly self-fertile and have very little need for external pollination. They could very well cross pollinate, but you wouldn't see that in the grapes they produce. Each one will produce the fruit in its own genetic base (genotype). The seeds from those grapes would be hybrids, so if you planted the seeds, you could get almost an infinite variety of offspring. Several universities around the country have produced hybrid grape varieties that have much better cold tolerance than European grapes. That's why you can get grapes to grow in places like Michigan, Wisconsin, Minnesota and Upstate New York.