EDIT: I've been beaten to it, but here's a bit more detail and a photo.
Can you gives us the profile of those trains? Wonder if the can be fiddled with to fit W12.
Different models have been built with widths between 2900mm and 3035mm (straight sides most of the way, not a maximum 'bulge' width), heights between 4200mm and 4400mm and car lengths of 20 to 20.5 metres. All Sydney electrics are double deckers with overhead wiring, and all are formed as four or eight car sets.
The most recent completed build order were the H Sets for outer commuter belt services of up to 162 kilometres long (Newcastle-Sydney) which feature seats for 432, wheelchair/bike space for 16 in the platform-level vestibule areas, and a toilet. The following image is copied from Wikipedia:
A reasonable comparison for the H Set (in terms of operating similar services) is the Class 375/377 - the length of a four car set is close enough to exactly the same for both, but the H Set is 230mm wider and 620mm taller. 432 people get seats in a H Set, compared to 236 in a four car Class 375.
To reduce the magnitude of works required down to just height increases, a UK-spec version of a Sydney-style EMU could be built to about 2750mm wide with 2+2 seating instead of the Sydney 3+2 layout, and you would still end up with approximately 360 seats in a four car set.