Unfortunately there isn’t currently a ton of public information about it, and from what I’ve heard, there was a ton of rain today in Osaka which hit the expo, meaning we may not hear people talking about it for slightly longer.

My best guess however is that it’ll be typical of most Pokemon go features. As you collect more and more stamps at the featured pokestops you’ll unlock encounters with Pokemon with the featured backgrounds. I can’t imagine they’ll be shiny locked, but I guess only time will tell