Let's define the setting options for when users share calendars with people outside their organization, as follows:

• Only free/busy information (hide event details): Selecting this will only share whether the person is available or not in a time frame
• Share all information, but outsiders cannot change calendars: This will allow external users to see all secondary calendar event details, including the guests list but not private addresses
• Share all information, and outsiders can change calendars: This will allow external users to see and update secondary calendar events, including the guests list and their addresses
• Share all information, and allow managing of calendars: This will allow external users to manage secondary calendar events