You can open a shared Google calendar is iCal by following these steps. If you already have the Calendar shared in the web-interface of your Google account, then all you'll need to do is add your iCal account.
A new window will pop up.
Change Account type to CalDAV.
Enter your Email Address as the User Name.
Enter your Password.
For the Server address enter https://www.google.com/calendar/dav/USERNAME@oc.edu/user - make the USERNAME the name of the calendar
For example - if the name of your calendar is shared.calendar the server address would be: https://email@example.com/user