Proposed date and time for all attendees of an Appointment

When a meeting invitee proposes a new meeting time, in outlook this information can be found in the "Scheduling Assistant" (outlook 2007):



Is there any way to access this information programmatically through the EWS API? The RequiredAttendees and OptionalAttendees collections of theAppointment allow me to find out whether and when the attendee has responded, but how can one access the actual proposed new time?