In Wyoming I believe you have to draw in order to buy the doe tags for the same unit you draw in. I could be mistaken but that seemed to be what we did this year. We could have purchased 4 or 5 doe/fawn tags along with the buck tag. 34 dollars each doe/fawn tag.
That's the way I understood it too when I researched WY earlier this year. I think maybe the OTC tags Yelp is talking about are the leftovers from units that didn't get enough applicants.
Actually, doe/fawn licenses are all independent of the any antelope license. You could potentially have six different licenses for six different hunt areas. All antelope licenses in Wyoming are limited quota, by hunt area.
Most public land hunt areas usually draw out in the license draw; private land areas are generally undersubscribed, with licenses available first-come, first-served after a certain date.