You can open a shared calendar and view others entries. First, they must share the calendar with you through Exchange.
Open iCal. Click the iCal drop-down menu and select Preferences...
Type the name of the person whose calendar you would like to view and select the correct person from the list. (Note: This person must first grant you permission to view their calendar)
The shared calendar will appear on the right side of your screen. You can click the name of the calendar, and view its content.
TIP: The name of the shared calendar will also appear on the left-hand side of the screen with a checkbox beside it. Uncheck this box to close the shared calendar. You can recheck this box later to view the shared calendar again.