In the Microsoft Email system, a calendar system is provided that allows corporate wide interaction and meeting planning. When creating meetings, you have the opportunity to invite those within your organization. As you do, you can use the scheduling assistant to show you whether the people you are inviting are available during your needed times. The system has an Autopick that allows for finding the best available time for all those required at the meeting.
While the various options for permissions and sharing permissions are many, this article deals specifically with the Free/Busy Time Privacy. For in depth details, see this video: http://youtu.be/8MsBWk0p7_M?t=12m50s.
To remove access to your Free/Busy time:
Keep in mind, this is one of many calendar permissions options available. Removing the default Free/Busy time will prevent anyone within the organization from seeing your Free and Busy time.