You can subscribe to any calendar that has at least Read permissions.
To subscribe to a calendar, perform the following steps:
Select Calendar from the service selector pane.
Click Create or Subscribe on the Calendar toolbar on the left pane.
Choose from the following options:
Create a Calendar
Subscribe to Calendar
Select Subscribe to Calendar.
The Subscribe calendar tab appears on the right pane.
Enter the user name or the calendar name to search in the text box provided.
A list of all users matching the search criteria are listed in the search pane.
Select the calendar that you want to subscribe by selecting the corresponding user name.
All calendars belonging to the user are listed in the right pane. For each calendar, the permissions assigned to the calendar are also provided. All calendars that are already subscribed by the user and those that cannot be subscribed by the user are disabled. These calendars cannot be selected.
Select the calendars to subscribe to by selecting the corresponding check box for each calendar.
Click Subscribe.
The selected calendar is added to the list of subscribed calendars in the Calendar service pane.