@Sean Thank you for the clarifying information. Apparently I was expecting the calendars fetching to happen by system.redrawInterval, which was set at one minute (60000 ms). Now I waited for 30 minutes and fetching happened and events were updated as I expected. No problem so far!
Seems to me that the [calendar].interval (fetching) is set to 30 minutes by default.
Now only one question remains: How can I change the [calendar].interval to for example 5 minutes? This is the interval in “default” calendar, and I have some events needing to be updated more often than 30 minutes.