Here’s a good article on the subject from my archive. 

Looks like several Utah towns, mostly smaller resort type communities, have done something along these lines, though I’m not sure how billboards are addressed (they are always a whole different animal, as you know). I think I heard Park City has some dark sky provisions in ordinance as well, though they are not mentioned in the article. You probably have connections with some of these towns, and maybe they are on the list server as well, and can respond directly. 

I’ve meet with a couple students working on the Dark Skies initiative at the University of Utah, mentioned in the article. I think they could be a really great resource. Stephen Goldsmith (I think, or maybe Reid Ewing) should be the point person/advisor on this research project. 

It’s great to see our small towns leading out on some really great planning work like this. Good luck and hope you’re successful. 

Regards -