It is now possible to create LDAP groups using Delegated Administrator. Groups have the following functionality:
A group is a list of users. The group does not “contain” the listed users. It is not a container.
A group can have a group calendar.
Invitations sent to a group reside on all the members' calendars, as well as the group calendar.
All members of the group share the same access rights to the group calendar.
There is no primary owner for a group calendar.