We are still considering the Voicemail on Busy feature for future releases, and will continue to update the status when it changes.
Note: The Busy on Busy feature has been released. Please see the following documentation for admin details:
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The team is working to address issues with call controls that occur for users running both Teams and Skype for Business. We will let you know when there is more to share.
The team has begun working on this feature. We’ll update as we have more details to share.