The funding source I've never asked for as it didn't interest me at the time - but for the economics of it, essentially the patronage numbers are a bit of a guess, especially in non-peak times. There would need to be significant mode shift of business and family travelers from taxis/uber (work reimbursements) and driving/long-term parking (convenience) respectively to properly (non-politically) justify removing a profitable bus service for a loss-making heavy rail line. Nothing particularly ground breaking about the logic - the most realistic option would have been to just have dedicated bus lanes for the entire journey, but we all know the competing interests over-ruling there
I agree with you gb274 that some red paint on the Tulla & MyKi integration would be by far the most cost effective way to provide a PT (albeit unsubsidized) service to the airport however the political reality now points to a train line.
I'm curious though in your thought that a diverted Bendigo line would be less cost effective than a stub line branching from Albion.
Would the extra cost of the greenfields track north of the airport not be offset in a CBA by the potential increase in capacity on the Sunbury line?
From my very basic analysis (and opinion), Bendigo via Airport is better than a branch line from Metro because:
*Sunbury Line will soon share with Melton and possibly Wyndham Vale/Tarneit, needs as many paths as possible (24+)
*Bendigo trains take up too many paths throughout the day, will only get worse as cities such as Kyneton become more commuter focussed.
*Bendigo trains if continuing to share with Metro trains will become slower, and less well patronised as a result
*VLine trains are more suited to taking airport passengers than commuter (Metro) trains, see Sydney
*The quicker the journey, the more people taken off the freeway in cars/taxis/ubers. Train will be faster running on RRL stopping pattern (Footscray/Sunshine/Airport) rather than Sunshine stopping pattern (West Melbourne/Footscray/etc./etc./etc./Sunshine/Airport)
*To increase RRL paths, can run Geelong via Werribee and Gippsland Trains through Southern Cross to Ballarat/Bendigo/Airport/Seymour as through services (think RER in Paris)
*Scope for 4 RRL tracks between Southern Cross and Sunshine if more paths needed.
*Scope for Seymour to run via rebuilt Albion-Jacana line on RRL
*Scope for SG tracks, more direct path into City for Albury/Sydney trains
I believe this option optimises the most solutions.
1. Ability to segregate all Metro traffic from VLine except Dandenong corridor (should have been done with CD9)
2. Provides Airport Rail with express path into city, Bendigo, Geelong and Gippsland trains would could all run via Airport (Ballarat and Seymour would need to change at Sunshine, hardly a diversion. Metro change at Flinders/Southern/Footscray/Sunshine which all trains would pass through).