Steps for subscribing to a Google Calendar from a group calendar: (Basically, you should copy the Private Address for iCal, which is found in the Google calendar settings.)
1. Navigate to Google Calendar.
2. Click the drop-down arrow next to the appropriate calendar, and click Calendar settings.
3. Near the bottom, find the Private Address, and click ICAL. A pop-up should appear with an address that allows other applications to fetch the calendar. Copy the private address.
4. Navigate to the hub, and sign in.
5. From your Dashboard, click the Groups tab and find and click on your group.
6. Once inside the group, click the Calendar tab.
7. Next, click Manage Calendars. Then, click Add Calendar.
8. Fill in the Title.
9. Paste the private address that was copied from Google into the URL field.
10. Choose a color for your calendar (optional). All events for that particular calendar will appear in the color chosen, or will remain black by default.
11. Choose Yes or No to publish to subscribers. If yes is chosen, people who subscribe to the group calendar will be able to see the events from this calendar in their subscription.
12. Click Submit.
13. To fetch calendar events, click the Refresh Option.
14. When you navigate back to the group calendar, you should now see that calendar appear.
Warning: At this time, a repeating event on a google calendar will appear as originally posted and does NOT reflect any changes made to that event. A ticket has been submitted and the web developers are working on the bug.