Additional cars will continue to be delivered daily and, once assembled, the first new subway train will undergo eight months of tests, the commission said Monday.
That means the first train could be put into service by the beginning of next year.
The 468 cars are being built by a Bombardier-Alstom consortium at a cost of $1.2 billion.
Commission chairman Philippe Schnobb admitted at a news conference he doesn't know yet if the new nine-car subway trains, which are 13 tons heavier, will consume more electricity.
The new trains can accommodate 1,068 passengers, compared with 990 for the current models, which have been in service since 1966.
"It's certain they will transport more people so, yes, there will be a different load," Schnobb said. "(But) we are not yet ready to say what difference that will make."
Schnobb also said an additional $1.2 billion will be spent to modify certain infrastructures and to train staff.
Schnobb reassured passengers after admitting that tunnels over a 200-metre stretch of the 71-kilometre subway system need to be shaved.
"These modifications are not because the trains couldn't pass through," he said. "They have to do with exceptional circumstances where there could be a problem with the pneumatic system accompanied by flat tires."
The commission said the work was already planned and was included in the total cost of the $2.4-billion project.
Montreal Mayor Denis Coderre said the subway cars will be more comfortable, more spacious, brighter and less noisy, adding they will revitalize the city's underground system.
He said that after riding the old subway cars for 50 years, transit users deserve to be spoiled with more reliable subway cars.
"If we want more public transit users, we have to show that they (the trains) are more efficient at every level," Coderre told reporters.
As in other major cities, such as Berlin, Mexico City, and Madrid, the new "boa" trains will allow passengers to move about freely from one end to the other.
All of the new cars are expected to be in service by the fall of 2018.
Meanwhile, a Bombardier (TSX.BBD.B) official said 150 workers who were laid off last fall at its factory in La Pocatiere should be recalled beginning this summer.
Sebastien Ross, the plant's manager, said with the start of delivery, mass production of the new subway cars will begin around mid-June.
The end of a contract with the state of Maryland for the delivery of 54 multi-level commuter trains forced Bombardier to lay off one-quarter of its workforce of 600 in La Pocatiere.