Microsoft posted a bit more information on the Cortana integration with Office 365
We’re pleased to announce the ability to integrate Cortana in Windows 10 with Office 365 for businesses, available in the latest Windows Insiders preview build. Cortana in Windows 10 will be now able to connect to Office 365 to help you accomplish more at work. You can preview this initial integration between Cortana and Office 365 starting today if your company is opted into First Release for Office 365, and you are enrolled in the Windows Insider Program and running Windows 10 preview bits.An early look at Cortana integration with Office 365
Today, Cortana is already great at letting you quickly see what your day is going to look like, see when and where you first meeting is, get a sense of travel times to work, or even get updates for upcoming trips from your calendar.