This week a leading think tank slammed the business case for the tram line, saying the territory government substantially overestimated the economic benefits of the project.

The Grattan Institute's report also noted the project was a key commitment in the governance agreement between ACT Labor and sole Greens Assembly member Shane Rattenbury – a fact certainly not lost on either the opposition or Canberrans more generally.

That the ACT government held onto a more positive expert review for 18 months only to release it the day after the Grattan Institute's critical report is telling.

While there can be little argument over the positive elements of the plans for the once-termed only ''aspirational'' tram line, now the territory is six months out from the local election the government needs more people on board with the business case.

Now a further two transport experts, one a supporter of the Gold Coast light rail, have weighed into the debate, backing up the criticism and saying wider economic impacts and land use benefits were an "incredibly high" proportion of the model.

Capital Metro Minister Simon Corbell maintains the two government-commissioned reviews of the business case show it is up to scratch.

"This government has been very clear: this is not just a transport project. This is a city building project," he said earlier this week.

That might be the case but there are still valid questions over whether a transport infrastructure project should be treated in this way.

There are still many who believe the scale of forecast wider economic benefits will never be realised, and if removed from the modelling the tram does not stack up at all.

The ACT government will only truly know whether Canberrans are behind the project come election day in October, but arguments are set to continue beyond then on the value of benefits the tram will bring.