Indeed, anyone using Outlook on Windows should be able to take advantage of the functionality provided by shared calendars.
Public calendars can be shared with anyone. To access public calendars, visitors need to use Calendar (or iCal with OS X v10.7.5) on a Mac, Microsoft Outlook on a Windows computer, or any other app that supports the iCalendar file format.
Private calendars can be shared with other iCloud users. Participants can view the calendar using iCloud Calendar, Calendar (or iCal with OS X v10.7.5) on a Mac, Microsoft Outlook on a Windows computer, or the Calendar app on iPhone, iPad, or iPod touch.
Followed Apple instructions but no luck. I have three accounts: gmail, apple icloud and exchange. Both gmail and exchange seem to allow sharing but when I try delegation on my apple icloud account it says "server wont support this" - to me that means that Apple won't support it. Confused. Maybe I am doing something wrong. What I wish to do is have a windows based colleague able to see my diary.