Found 15th FebEdited by:"Silurianxx"
Based on feedback this beta is open to all, you just need to download Xbox Insider Hub then navigate to Insider content. If you don't know what this is it's an app on the Xbox One, I've put a link in the description which explains how to download it. It looks like it's playable from 10am tomorrow and is available for 48 hours. I'm downloading now :-)