The crazy thing is that much of this will depend on which airline issued the ticket. As an example two pax are travelling on the VS/DL code share flight LHR-ATL and both are connecting to a DL flight ATL-DFW. One pax has a VS issued ticket, the other a DL ticket.
The flight is delayed and the pax misconnect. The next available flight is AAs. The pax with the VS ticket can be rebooked onto it, but not the passenger holding the DL issued ticket.
I really hope these guys know what they're doing.