It was said tonight in a tweet by the CBS All Access Twitter account that the service will be getting Apple TV Channels support starting on July 29, 2019.
Hi! Thank you again for your interest! We wanted to update you and let you know that the CBS All Access Channel will launch on Apple TV Channels on 7/29! Happy streaming! 😊
— CBS All Access Help (@cbsaahelp) July 25, 2019
As for how much it will cost is still currently unknown. The good news is that the Apple TV app is available on the iPhone, iPod Touch, iPad and Apple TV. It is set to come to the Mac in macOS Catalina once that is released this fall.
macOS Catalina is set to get rid of the iTunes app and its replacement will be three separate apps, which are going to be the Apple Music, Apple Podcasts and Apple TV apps. The Apple TV app is how you will get access to Apple TV Channels from the Mac.
The billing for CBS All Access is all done right through your Apple account, meaning that if you subscribe to a service like Apple Music or Hulu through your Apple account, an Apple TV Channels subscription will also go in that same area.
It is also unknown if CBS will add any sort of exclusive features to being on Apple TV Channels. HBO NOW does include the ability to download and watch content offline.