You can add any publicly-available Trumba calendar to your Google Calendars list, as long as the Trumba calendar is published without password protection.
Note After the Trumba calendar is updated, it can take up to a few hours for the changes to appear on your Google Calendar.
In Google Calendar, you have the option to add a publicly-available Trumba (or any .ics) calender to the Google Calendars list.
The URL should look like "webcal://the_calendar_URL.ics" -- where "webcal" replaces "http" and ".ics" is added to the end.
For a fictional Trumba University calendar, for example, the URL might look like: "webcal://www.trumba.com/calendars/trumba-u.ics" in Google Calendar.
Tip For more information, go to Add someone else's Google calendar in Google Calendar Help.