The state government is, shall we say, not on board. They are talking $10-15 billion for the project - and yes, that's a "b", so presumably the business case is being done with the same Monopoly money as airport rail. Mind you, I did think $4b was a little on the low side for whatever was actually being proposed.
Frankly I have no idea who is talking more nonsense, Ms Allan or Mr Tudge, but I'm inclined to listen more to the state government because a) they've actually managed to do a few things these last years instead of whatever the feds have been doing, and b) they aren't trying to win an election.
With that in mind I'd hazard a guess the state wants $10b to do the job properly by sparking and quadding to WV and Melton, plus a new Sunshine-CBD route, but ScoMo's apparatchiks have told him $4b will cover an extra track pair from Sunshine to Geelong, with no auxiliary works.