So the last cars would have been towed by a loco (probably part of a regular freight train?) on SG transfer bogies to Adelaide. So probably something like, drive (or loco hauled) out the factory gate in Dandenong, to Melbourne City, bogie change to SG, hauled to Dry Creek, and be reunited with original bogies.
Wonder why they aren't doing the same with these new cars. Is Adelaide's loading gauge really different enough to prevent the new cars being hauled up the Dandenong suburban line, given the 3000 series are externally very similar to Melbourne electric comeng trains?
What is the exact length of the individual new cars? Is it the same as the VLocitys? Do they share the same external dimensions?
They are, according to a DPTI fact sheet, 3.050 metres wide (same as Wiki says about a Comeng) and 75.72 metres long (significantly longer than 71 metres for a Comeng) and we don't know if all three cars are exactly the same length yet. The lower part of the body doesn't appear to be as tucked in as the Comeng/3000 cars either, which could make a difference with platform clearances. My guess is that the length (especially the long nose) would cause problems in Melbourne around curved platforms, and that there would have to be numerous clearance-testing runs before it would be allowed to happen by the network regulator.
There does appear to be some cosmetic similarity to the VLo, but all that suggests is that Bombardier may have hired designers who had previously worked on new models of the Porsche 911. There are also clear differences as well, both visible and quantifiable, the A-City EMUs are 130mm wider (a significant amount when working with clearances on curved platforms) and don't appear to be tapered at the vehicle ends like a VLo. The body is an all-new design that is the first in Australia to comply with newer UIC crashworthiness standards, it's logical to expect it won't be exactly the same shape.
It doesn't matter anyway, the road delivery method using a roll-on/roll-off trailer is so significantly easier that nobody in their right mind would have selected the bogie transfer method for a short 800 km hop. All you need is a big flat truck, a ramp and a tractor or winch - compared to three sets of barrier wagons, lifting jacks, transfer bogies, multiple clearance runs and so on.
If we had a more generous loading gauge on the interstate line then the convenience might have tipped the way of using rail, with them loaded on a roll-on/roll-off flatcar to avoid mucking around with bogies. Even then, that doesn't resolve the loading gauge issue between Dandenong and the standard gauge freight terminal (or the need for set of barrier wagons for each city), and if you need road transport for that sector you may as well just keep going and use it for the full journey all the way to Seaford.