"Google's CalDAV page already lists the API as being "deprecated." A note on the page adds "If you think you have a compelling use case and would like to be whitelisted for the new version of CalDAV API, please fill out this form."
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Google, however, confirmed this will not impact the agreement with Microsoft and that the Softies will still be able to implement CalDav support on Windows Phone."
That article, and many of the others linked from within show that it is very unclear what's going on exactly. It would appear that Microsoft is only planning on implementing CalDAV in Windows Phone but has, as of yet, not confirmed it.
It does appear that they have confirmed not supporting CalDAV on Windows 8, RT, or Outlook. And since Google is phasing out support for ActiveSync come 7/31/2013, the only way to sync with Google calendars and contacts is from Outlook 2010 and earlier, and only if you are a paid apps user. (using ActiveSync)
...
Google, however, confirmed this will not impact the agreement with Microsoft and that the Softies will still be able to implement CalDav support on Windows Phone."
http://www.zdnet.com/microsoft-in-the-clear-to-add-google-ca...