This link will add the Pack calendar to your calendar using iCal format: https://calendar.google.com/calendar/ical/bt1jiggdc6nl1c90itkbsm8jl4%40group.calendar.google.com/public/basic.ics
You can also subscribe to the calendar at the following address: bt1jiggdc6nl1c90itkbsm8jl4@group.calendar.google.com
Read how here: https://support.google.com/calendar/answer/37100?hl=en