with regard to R44's statement "...there's a couple S Sets at eveleigh that are always there..." - that is fairly accurate.
There are usually 2 x trains tabled to be stabled at Eveleigh on weekdays after the morning peak for the purpose of training and return back into service for the afternoon peak. Usually the training facilitators prefer to have 2 different sets, ie 1 x Silver Set (S,K or C set) and 1 x Tangara, so they can teach/demonstrate the specific differences unique to them. However due to operational requirements, sometimes the operations supervisors cannot always fulfill Railcorp Training's preferences/requests. Thus, they often end up with 2 x S Sets. (something is better than nothing)
Likewise, there is a daily (weekday) train tabled to be stabled at Lavender Bay Car Sidings for training. That one varies between an S or K set.