By default, all users have access to the free and busy times for other users; however, a user must have permission to open another user's appointment book or to view details of another user's busy times. A user can grant permissions for access to his or her appointments, contacts, events, or tasks to another user. However, a user does not have access to Schedule+ items marked Private unless the user is an owner or delegate owner on the item.
To set up access to a user's schedule
To view another user's schedule