If the 2000 Class aren't permitted under the wire (and I still can't see why not as you look at a Cityrail V set, and its double deck where the passenger at at the same height as the driver of a 2000/2100 etc),
This has been done to death. There are two
significant problems with this.
1. Our lines are high voltage AC, those in Sydney are low voltage DC which allows for narrower clearances. The lines in Sydney might also be physically higher given their use of double-deck EMUs, but I don't know the exact height of either our lines or theirs.
2. The double-deck EMUs used in Sydney are (not surprisingly, being E
MUs) designed to be compatible with electrification right the way through, with the roof being properly earthed in case of an arc or a live cable coming down. The fibreglass canopy on the 2000/2100 cab is not safe from either an arc, the electrical issue of being hit by a live cable or the physical damage caused by a downed cable slicing through it.
If a 2000/2100 consist was scheduled to be sent onto one of the southern lines I expect that drivers would walk off the job en masse, and quite rightly. That's okay though, because the 2000/2100 class can still keep running on the northern lines to Outer Harbour and Gawler.
... it means that you'd need 15-17 sets of 3000 class railcars, in various configurations, just to cover the temporary timetable used up until the closure, until sufficient electric stock in online. Add in another 2 sets for Tonsley, I'm not convinced that a full functioning service can be resumed with the current fleet, discounting the electrics.
The last full
timetable on the Noarlunga/Tonsley line (up to the start of February 2012) required a maximum of 13 consists in service at one time, including consists in the middle of a layover between two service runs.
The increases to the Outer Harbour and Belair lines were not really that significant (mostly just a rather average spin job), and I'm sure that with the full use of all ten 2000/2100 consists and the temporary shortening of some 3000/3100 consists by one car there would be ample stock available to not only resume a full schedule to Noarlunga and Tonsley but also to extend most trains to Seaford, or at worst run a Noarlunga-Seaford shuttle. It might lead to some services being quite crowded (i.e. Outer Harbour line people might get the rude shock of needing to sit next to strangers) but it would still be the best immediate step to get rail running again and stop fluffing around with substitute buses or leaving perfectly good new stations gathering dust while blocked up by fences.
As each EMU enters service, a 3000/3100 set can be cascaded off the Seaford line and go back to providing higher capacity on the other lines. Once enough have entered service that capacity on all the other lines is back to normal, adding in extra trains becomes an option.