Mary Jo Foley has a short write up about CalDAV over on ZDNet.
Some notable quotes from that article.
"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."
"The Windows team is not going to be adding CardDAV or CalDAV support for users who are trying to connect to a Google account via Mail/Calendar/People after January 30. Here's Microsoft's guidance as to how these users can sync their Google accounts with Windows 8 and Windows RT."