Imaging you have a group with 2 members and all are required for meeting to take place and proposal preference is set to Notify & Hold.

In this case, any of group members can accept and manage proposal.
All of them will receive an email notification.

Each of the participating group members can then choose to accept the proposal using the Accept link in the email notification. When they do so, they become the meeting organizer and the event is created on their calendar. Other group members are added as required attendees.

All participating group members can still manage the meeting even after it has been accepted and they will see it listed on their Agenda page. As any changes are made to the meeting, the original calendar event is automatically updated.

As an example, consider the case where your colleague John accepts a proposal made to a group but then is out of office when your client is requesting a change of the meeting time. Ordinarily, only the organizer could make changes to the event.
With FreeBusy, however, any participating group member can make changes to an accepted proposal on the organizer's behalf.