When the WA Labor Government of the early 2000s started building a passenger railway through large stretches of undeveloped land all the way from Perth to Mandurah, plenty of opponents questioned why.

"You get a situation where you're amongst cattle and those cattle aren't going to be travelling," businessman Willy Packer, a prominent figure in the behind-the-scenes operations of the Liberal Party, said of the 71-kilometre route.

It was a common refrain from members of the Liberal Party of the time, with one frontbencher saying the Labor government should "can the whole bloody project" and another labelling it an "absolute waste of money".

"The government is trying to con the people of Western Australia into believing they need a railway line when they do not," then-Liberal MP Paul Omodei said in 2002.

In WA politics, it seems the more things change, the more they stay the same.

Perth's most used train line

A decade and a half later, the transport debate being had is eerily similar to the one had about the Mandurah line — but this time about the projected $863 million Ellenbrook rail project.

Then Planning Minister Alannah MacTiernan and Premier Alan Carpenter celebrate the arrival of the first train to Mandurah in 2007. ( ABC )

Just like before, a Labor Government wants to spend a large sum of money on a railway to a growing — but still not-fully-developed — area on the outskirts of Perth.

And, just as before, elements of the Liberal Party believe the expected substantial cost is unjustified because the population on that corridor cannot sustain a train line.

"It should be built some day, but in 15 years and not today," Liberal leader Mike Nahan said recently.

Of course, most would now see the criticisms of the Mandurah line project from 10 to 15 years ago as wide of the mark — at least with the benefit of hindsight.

It is now Perth's most used rail line, with its 20 million boardings each year putting it well ahead of the second placed Joondalup service, and has served as a vital link into the city for those in a stretch of suburbia which grew rapidly.

It is hard to imagine what Perth would be like today without the Mandurah rail line. ( Peter Major: User submitted )

The project certainly did not come without its fair share of problems, with cost blowouts leaving the state with a $1.6 billion bill — about $2 billion in today's dollars — and construction down the centre of the Kwinana Freeway causing congestion headaches.

But the prospect of cattle roaming sparse farmland either side of a little-used railway, as Mr Packer argued, is long gone.

"It is one of the most successful rail projects in Australia," Transport Minister Rita Saffioti said.

"We have seen massive developments along that rail line and enormous patronage."

Ellenbrook different: Opposition

Nonetheless, the Liberals see clear distinctions between the Ellenbrook plans and the results seen from the Joondalup and Mandurah developments.

Deputy Liberal Leader Liza Harvey says Ellenbrook is different to other rail projects. ( ABC News: Andrew O'Connor )

"The problem with Ellenbrook is it is not a commercial centre, it is a residential centre," shadow transport minister Liza Harvey said.

"You do not have those additional commuters who would be making use of the line."

Even few Liberals would dispute now that many of the criticisms their predecessors lobbed against the Mandurah project look, 15 years later, somewhat foolish.

The Government believes hindsight will be similarly unkind to those talking down the Ellenbrook project.

"It would be ludicrous to think that Ellenbrook is not an important centre," Ms Saffioti said.

"It needs a train connection."