Current issues to Comeng refurbishment:
1) Bogie lifehttp://www.theage.com.au/victoria/cracks-found-in-metro-train-bogies-20131223-2zumq.html
This one came to general attention last year through a leaked Metro report. Note that the bogies mentioned are the LHB type - which are the later batches.
2) Bodyshell status and life
Following on from the fleet split, the works to reunify the fleet, and a lot of other addenda to the fleet (such as digital train radio) the interior is significantly different to its original fit and fitment. Assessment of the existing fleet's bodyshell suitability to undertake a proper life extension, in terms of value for money. For example, if the bodyshell would, based on an engineering assessment, only last another 10 years past the current life before displaying unacceptable levels of wear and tear, the work to refurbish the entire current fleet of over 550 carriages may not achieve the desired cost savings of a full 35 year lifespan of new fleet.
3) Ease to refurbish to improve to 21st Century requirementshttp://www.therailengineer.com/2013/11/28/class-317-half-old-half-new/http://www.railwaygazette.com/news/traction-rolling-stock/single-view/view/re-engineered-emu-offers-new-train-for-less.html
Bombardier, at the behest of Angel Trains in the UK, did a refurb of a four car class 317 EMU, which is of a similar age to the Comeng. This shows the potential for life extension and what could be done with existing rolling stock. Significant replacement of existing electrical and propulsion equipment may affect the overall cost/benefit equation.
To sum up:
a) There are issues that are not insurmountable for the Comeng fleet if a proper full life extension was to be conducted.
b) The benefits of refurbishing the existing fleet have to be considered in light of costs - such as how much of the of the existing hardware is retained and what is renewed.
c) What are the predicted benefits to fleet reliability, performance and availability? What are the predicted benefits to operational costs?
d) A comprehensive vehicle refurbishment and life extension has been conducted elsewhere, so analysis of these projects would provide a further basis for developing a case.
I note that Victoria hasn't had the best history for "rolling" these projects out -
B Class locomotive refurbishment to A Class ended in favour of newer fleet of N class locomotives when costs between one or the other was negligible
Harris refurbishment to provide similar amenity to Comeng ended. I'm unfamiliar with WHY this was ended, but I could imagine the various issues of having to remove asbestos from insulation, upgrade wiring and interior to support air conditioning, would've been more complicated than ordering another batch of Comengs at the time.