As a user, viewing an event in an event calendar is offering cumbersome user experience:
  1. Click on event in calender opens a small tag sort of view with some basic informations.
  2. Click on the event title opens the event detail overlay view - in the event portal - in a new tab.
  3. Click on the event page opens the Confluence page - in a new tab.
I would expect that the calendar offers the same experience as the event list or any other event integration: Clicking on an event opens the event detail overlay in the page context of the calendar. Opening the event page in a new tab is OK, of course.