Sumatra Development leads the field of migrating entire calendar servers to Exchange. We migrate Oracle Calendar Server, Oracle Beehive, Apple iCalendar, and Zimbra to Microsoft Exchange keeping all meeting information and resource bookings intact. We migrate calendars server-to-server between Exchange and Office 365 while keeping meetings live and doing incremental syncs quicker than any other solution.
You guys might remember our earlier posting on DAVical migration to Exchange / Office 365. Well, we went ahead and started it based on a request from Europe. If there's anyone else out there who's looking for this please drop us a line.