Minister for the Capital Metro Agency Mr Simon Corbell told more than 300 local, national and international representatives at an industry briefing for the project on September 15 that the government would issue an invitation for the expressions of interest on October 31.
Corbell says the cost of the project will be determined by the tender, but the estimated investment will be $A 610m ($US 549m) with a $A 173m contingency.
The project will be implemented as a 20-year build-operate PPP with no financial contributions from the ACT government during the construction phase, although it reserves the right to inject funds at a later stage, for example to reduce the project's debts.
"Although it is unusual to release a project's business case, the ACT government is committed to an open and transparent process and intends to release the Capital Metro business case next month," Corbell says.
The 12km line will run from Gungahlin to the city centre, with 13 stops and a service frequency of 10 minutes on weekdays and six minutes at peak times.
Smart ticketing will integrate the line with the Action Bus network with contactless fare collection terminals situated in stations.
At the briefing, it was suggested that catenary-free vehicles could be considered as an option and Capital Metro are not mandating overhead power supply in the tender, looking instead to prospective bidders to offer innovative solutions for traction power supply.
Construction is expected to begin in 2016, with services commencing by 2020.