To see this calendar in Outlook one can do the following:
In Outlook, click File > Account Settings > Account Settings.
On the Internet Calendars tab, click New.
Paste the following address into the field that appears: https://www.google.com/calendar/ical/853r4ik5hg283aprtrme9q5pjo%40group.calendar.google.com/public/basic.ics
In the Folder Name box, type the name of the calendar as you want it to appear in Outlook, and then click OK.
Restart Outlook.
On a Mac:
In your calendar app, go to File>New Calendar Subscription
Paste the following address into the field that appears: https://www.google.com/calendar/ical/853r4ik5hg283aprtrme9q5pjo%40group.calendar.google.com/public/basic.ics
Give it a name and you're done.
On an iPhone/iPad:
Go to Settings>Mail, Contacts, Calendars>Add Account>Other>Add Subscribed Calendar
Paste the following address into the field that appears: https://www.google.com/calendar/ical/853r4ik5hg283aprtrme9q5pjo%40group.calendar.google.com/public/basic.ics
Give it a name but leave username and password empty, and you're done.
Please let Tobias Klein know when you experience problems.