I would be amazed if the permanent coupling between the first and second car could be done outside in the yard like that.
These are not old-style railcars that can be coupled and uncoupled at will; these are permanently coupled cars that, once coupled, operate as one unit. Many of the various systems involved are by no means duplicated on each of the three cars that make up one unit.
A road-rail vehicle of some kind (using rubber tyres for better traction) might be more suitable for getting the centre car into the commissioning shed in the absence of a 3000-compatible coupling on either end.
Agree about the rubber tyred vehicle, they seem to work quite well moving three ballast hoppers, about the same or more mass as a three car EMU. A new way of getting EMUs to Dry Creek Depot.
Having the Goal Loop would help.