You can add the GTS Master Calendar under your calendars in your Google Apps account. Here is how to do this. (Please note: Google Apps does not have the capacity to universally push the Master Calendar to all accounts, each account holder will need to subscribe to the calendar.)
Go to the Master Calendar at http://www.gts.edu/mastercalendar and with your email account open, click on the + Google Calendar link in the lower right corner under the calendar.