At the end of January 2013, Microsoft and Google came to a last-minute agreement to extend Google's support of Google Sync, which is built on Microsoft's Exchange ActiveSync, until July 31 -- instead of terminating it by the end of January, 2013, as previously announced. In the interim, Microsoft would build support into the Windows Phone operating system for CalDAV and CardDAV, the Google calendar and contacts sync protocols, the companies announced.
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."
I asked Microsoft officials if the Windows Phone team was among the whitelisted developers. No word back so far.
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.