Unfortunately, as an email reflector, Outlook is unable to expand the list to show each list member or their availability.  Meeting organizers can add a PantherList to a calendar invitation and they will receive the meeting invite, but the organizer will not know who is and is not planning to attend.  

As a workaround, meeting organizers can enter each attendee in the meeting invite or create a contact group containing all attendees and invite the entire group.

Instructions for creating contact groups are available on Microsoft's People overview page under the "Create a Group" heading.