Nubiles has promo clips especially made for tube sites.
According to the new 2257 regulations coming out, secondary producers must have the ids for all the content on their site. Maybe if the tube site is just hotlinking all the videos from the sponsor it wouldn't need it. What I have seen pornotube do is have a text link to the program's 2257 page below the video, that is probably the best solution for right now.