Cross-rail is an enormous project, just huge. One side of London to the other while connecting lots of existing lines and stations together - the fact that they've managed to pull it all together in such a short period of time is testimony to what can be done when governments decide that they actually want to get it done.
Not in our case, sadly...
A thing to keep in mind when comparing Greater London and Greater Melbourne is both the population and area of both cities
Greater Melbourne has a population of around 4.3 million (2013 figures) and an area of around 10,000 sq kilometres.
Thats an area equivelant to roughly 100 kilmetres by 100 kilometres
Great London However has a population of 8.1 million (est 2011) and an area of only 1569 sq kilometres.
This is aproximated by an area 40 kilometres by 40 kilmetres.
Population and area figures from wikipedia.
London has double the population in less than 16% of the area of Melbourne, this would make funding of large scale projects a far easier task.
Greater Melbourne is one of the most spread out (low population density) metro areas in the world the people of Melbourne need to understand this as the only way decent infastructure can be built is by the population forking out the funds to do so. This means higher taxes. there is no other way........
Probably in the end a better way forward would be to increase the density of housing in the inner metro areas (say area covered by the tram network) to something equilvelant to most other suburban areas.