I'm on a Cingular HTC 8525 phone. Using the airwaves or using ActiveSync over USB to a windows box does not pull in details from any secondary or share-mounted calendars.
My VIPs delegate their calendar to an assistant, but they want to be able to "hide" some appointments. We've told them to use "Calendar" for most items and create a "Personal" calendar with free/busy unchecked for personal items.
If they could not sync a 2nd calendar another possible option could be to tag appointments as "private". Private appointments would not be visible to someone even if they have manager rights to my calendar. This would be a Zimbra enhancment, and I don't know how that would affect outlook clients.
Perhaps the appointments from each calendar could be merged into the one calendar available on the mobile client. I don't know if each appointment has a UUID. If it did then the mobile client could successfully edit appointments on a second calendar even if it wasn't smart enough to create them.
Where exactly is the limitation preventing the 2nd calender from syncing? Is it a limitation of the mobile Outlook client? A limitation of the Active Sync software? Zimbra?