Hello Tony,

You are correct that you would need the enterprise edition to share calendars with other users on you domain.  Users will need to login to the web interface to shared their calendars and then to map any shared with them.  Once this is done they can use Add to Outlook to get the shared calendar into Outlook.  Although this will not add the calendar to the native Outlook calendar, it will in Outlook listed as a separate calendar.  At this time only the calendar owner, and those invited on the calendar event, will receive a reminder.