There's a way to edit a calendar that's super hidden (I don't even know where to find it anymore minus that it's in my history) called My Calendars at /wiki/calendar/mycalendar.action. From there, you can remove added calendars and edit a variety of features that aren't allowed from an embedded calendar.
Is there a way for me to share ownership of those calendars with other users so that if they were to go to that same page, they would be able to see the shared calendar?