Some shared calendars have multiple sub-calendars associated with them (e.g. the Room Assignments Calendar). However, when you try Adding a shared Calendar into Outlook, you only see the default Calendar, and none of the sub-calendars associated with it.
In order to see the sub-calendars of a particular shared calendar, use the following procedure.
In Microsoft Outlook, click File > Account Settings > Account Settings
Double-click the row in the box (Note: this may appear as your email address, or simply Mobap).
Click the Advanced tab. Then, click Add.
Note: To remove a shared calendar, you would simply select the calendar from the list on the left and click the Remove button.
You will be prompted to Add mailbox. Type the name of the mailbox you wish to add in the box (in this example, we are adding the Room Assignments Calendar mailbox), and click OK. If you were successful, the mailbox you just added will appear in the list.
To finish, click Apply, OK, Next, Finish, Close.
Clicking on your calendar should reveal all the sub-folders of the shared calendar you added. Again, in this example, you are seeing the Room Assignments Calendar.