More Dolby Atmos workflow guides for Content Delivery from BBC Studios and Amazon MGM are avalaible now, here's the links you need.
BBC Studios:
https://www.bbcstudios.com/media/6914/contentdeliverybook.pdf
Amazon MGM Studios:
https://portal.amazonstudios.com/hc/en-us/articles/15986845319323-Asset-Technical-Specifications
The mixing guide from HHB is here:
https://www.hhb.co.uk/wp-content/uploads/Dolby-Atmos-Music-Mixing-Guide-.pdf