This is something that's more specific to skinny tire racing.
Women can generally race in men's races if the so chose.
The only real exception would be men's pro only races. Some of the women on the team I race for here in FL often will enter men's criterium races to get an extra hard workout in addition to their own women's race. I think only a couple of the other women racers in the huge pack had any idea what the hell I was doing. The men seemed clueless. This is something that's more specific to skinny tire racing.