http://blogs.technet.com/b/lystavlen/archive/2011/11/29/free-busy-viewing-and-calendar-sharing-in-office-365-hybrid-environments.aspxWe often get the question: "For Office 365 organizations in a hybrid Exchange deployment (some users on-premises, some users in Exchange Online), what Free/Busy viewing and Calendar sharing options are available?" In the below table you'll see whatsen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)