In the Pro version, just add Network Shared Calendar and point the URL to something like
https://mailserver.my.domain/home/us...lendar?fmt=ics.
There no need to import and export. Rainlendar2 pull the ical directly from server.
I also recommend turning on "read only" flag, even though rainlendar2 can put events back into the calendar, it may overwirte changes/exceptions in the reoccurring meetings when you are update/adding other meetings to Rainlendar. Work best just for monitoring and notification.