Last I read all ranch bison have the ear tags mainly to show medical testing and back ground checks. And a ranch bow hunt are not a walk in the park especially compared to a rifle hunt, rifle hunts are much easier. Trying to get in to bow range is a task in itself and then you're in range for them to turn the tables on you. Bison kill more people than bears do. To put one down with one well placed arrow is not the norm, plan on having a full quiver and it might be empty when the bison is done.
The three wild herds I know about are spread out, one in Canada, one in Wy., and one in Arizona. Drawing a tag is difficult for anyone of these wild herds for a trophy bull hunt.