If your organization uses Google Apps as mail service but you are using Evolution, there is no evident way to view and edit shared group calendars until recent versions. To add group calendar you need:
- go to calendar settings on web
- Calendar Address: -> ID (somenting like firstname.lastname@example.org)
- Evolution -> New Calendar -> Google
- User name -> this ID
- Auth with usual name-pass or other means you use (Kerberos, OTP) in the window appear.
- Allow Evolution to use the Google’s resources.