In certain situations where event information is sensitive, it may be preferable that users can see if someone is free/busy, without knowing exactly what is keeping them busy.
This type of situation is supported by the iCalendar VFREEBUSY object type.
The object type is used by Google Apps calendars where the organisation has prohibited the public disclosure of event information.
Team Calendars should support the VFREEBUSY object type in import files and also in the subscriptions.