I mentioned a few weeks ago that Microsoft publically announced support for using Exchange Server as a repository for Cloud PBX voicemail.
Now a few more details have surfaced on TechNet (thanks Nick Elniff from the Modality team for flagging).
Interestingly the voicemail service is being referred to as Cloud PBX Azure Voicemail in this article.
Cloud PBX Voicemail with Exchange Server Supportability Matrix
Configuration steps are provided on the TechNet Article.