Gehrt does bring up feral dogs which, for obvious reasons, would be more likely to mate with a coyote than a domestic dog. He says that in places like the Southeastern U.S., where packs of wild dogs are more common, the chances for interbreeding go up slightly. But even then, Gehrt points to the different breeding cycles that coyotes and dogs have. Dogs can breed year-round, he says, while coyotes only have a narrow breeding window during the winter months.
What he doesn't mention in this paragraph is. A dog can also come in heat during the same months as coyotes do.