A key feature of Sunrise is ""Users can access their calendars from Google, iCloud, and Microsoft Exchange, as well as connecting to a wide range of other third-party apps. "
Microsoft clearly understands that data-portability is becoming a major feature / factor in purchasing decisions.
Google, on the other hand, keeps trimming portability - particularly with MSFT.
In august, for instance, they killed Google Calendar Sync which made for simplified syncing with Outlook Calendar. (1)
If portability is what's driving this acquisition and strategy I am excited to see what's coming next.
(1) https://support.google.com/calendar/answer/6054804?hl=en