Like most infrastructure - e.g. electricity lines, telegraph...

Like most infrastructure - e.g. electricity lines, telegraph lines, road and rail - pipelines stimulate economic activity along their route. 3 of the 4 proponents aren't dependent on government funding - i.e. the tax payer. They just need approval to proceed. Therefore the best economic outcome for Australia as a whole would be to give the go-ahead for both the northern and southern pipelines on a self funded no subsidy basis. This would also be good for CTP as given time it could very nearly find enough gas to fill both pipelines itself. They pipelines will also be able to carry gas from the Timor sea.