To modify the properties of a calendar, use the cscal utility modify command.
For example, to change the group scheduling access control settings of AllAdmins and
specify RJones as another owner:
cscal -a "@@o^c^wd^g" -y RJones modify AllAdmins
-a "@@o^c^wd^g" grants owners write and delete
access to the components (events and tasks) of AllAdmins.
-y RJones specifies this user ID as another owner.