Montreal's original subway cars are set to retire after 50 years of service -- and the city's transport agency is looking to members of the public to give them a second life.

The Societe de transport de Montreal recently issued a call for proposals from members of the public who would like to buy and transform the first-generation cars, which are set to be gradually replaced over the next three years.

"We thought it would be a good idea to offer the public the opportunity to give us some ideas of what we can do with those cars," said the agency's chairman, Philippe Schnobb. "If there is any possibility to reuse (them), protecting the heritage of the metro, we're open to ideas."

To be approved, a project must be feasible and environmentally friendly, include financial planning and honour the cars' legacy.

Successful applicants can buy one of the cars for either $750 or $1,000, plus the cost of shipping, which is estimated at around $4,000.

Although the news has generated significant buzz on social media, experts warn finding new uses for the cars won't be easy.

While other cities have turned old train cars into restaurant and exhibit spaces -- or in New York's case dumped them into the ocean to create artificial reefs -- most of those ideas aren't feasible in Montreal's case.

Because the subway system operates entirely underground, the cars were never designed to stay outside, let alone withstand harsh Canadian winters.

The process of winterizing them could be prohibitively expensive and would probably mean significantly altering their signature design, according to several architecture experts contacted by The Canadian Press.

Schnobb, acknowledging the concerns, says the transit authority will only approve projects that take into account both short- and long-term maintenance costs.

"We don't want to have trains in the field in 10 years from now rusting, so we want to make sure those projects are durable," he said.

One group from the city's Mile End neighbourhood has proposed using several of the cars, placed end-to-end, to create a pedestrian walkway over a stretch of railroad tracks where illegal crossings are common.

"As New York dumps its outdated wagons in the ocean, we will give them a new life while solving an urban problem," reads the website for the project, whose name translates to "walkway of possibilities."

The two-ton, blue-and-white cars have been a mainstay of the city since the first one rolled out on Oct. 14, 1966, and the system was pronounced up and running by French cabinet minister Louis Joxe.

The opening ceremony included an 11-piece brass band, a blessing by Montreal's archbishop and a crowd of 5,000 enthusiastic citizens and dignitaries, according to the Montreal Gazette's archives.

But after 50 years of service, the old trains will be replaced by new ones at the rate of about one a month, leaving around 336 cars looking for a new vocation.

Montreal is not alone in deciding what to do with outdated transit infrastructure. Several other cities including Toronto, Edmonton and Calgary are also upgrading their rolling stock as their systems hit the 40- or 50-year mark.

A spokeswoman for the Edmonton Transit System said the city is looking at ways to dispose of its oldest light rail cars "in as an environmentally sustainable fashion as possible" when they are decommissioned in 2025.

Toronto has sent most of its retiring subway cars to scrapyards and a spokesman for the city of Calgary says it will likely do the same with the 25 trains slated to retire this fall, including five that will be stripped for parts.

Staff at the Universite de Montreal's faculty of environmental design say they are considering whether to hold a multi-disciplinary design contest for students who want to mount a project with one of the Montreal cars.

Prof. Anne Marchand says the size of the cars and the requirement they stay indoors mean most proposals would probably involve preserving them in pieces -- a controversial topic in the design world.

Regardless of whether the school moves forward with the contest, she hopes the discussion with students will include not only questions of how to preserve and for how much, but also whether such a project should be undertaken at all.

"Is it appropriate to reinterpret objects in this way?" Marchand asked. "It's an interesting object of study."

Schnobb acknowledges that the difficulty in reusing the cars means there won't be many buyers.

The transit authority will keep three cars and one has been promised to a railway museum, but the bulk of them will end up being recycled for scrap.

The deadline for submitting proposals is June 1, and the agency hopes to announce the successful projects by this fall, in time for the subway's 50th birthday.

"People have a big attachment," Schnobb said. "For some people, they have been living their whole life with those trains."