I'm not a lawyer, but I'll play one on the internet.. I have a friend who is a photographer who said that anything that can be seen with your eyes can legally be photographed. It may be different on private property, so they may be able to restrict photos, but more likely, due to the sheer number of cameras that are present at any given moment at a Disney park, if an entity has reason to restrict photographs of something at the park, they would only be able to restrict/limit Disney Photogs from taking pictures of it. Or it could be part of an agreement to share IP.