For a railroad track that hasn’t been used in years, Track 61 sure has a lot of important fans.

The roughly 1.5-mile spur cuts across the Seaport District from the southwestern edge of South Boston. Former Governor Deval Patrick’s administration had wanted to revive it to shuttle conventioneers between the Seaport and the Back Bay; Mayor Martin J. Walsh’s administration suggested connecting it to the MBTA’s Fairmount Line to extend commuter service to the Seaport.

Now the track is coming back to life for an entirely different use: testing new Red Line subway cars that are being built for the Massachusetts Bay Transportation Authority in Springfield. The MBTA recently decided to invest $32 million to revive a portion of Track 61 from the Cabot Yard repair facility near Broadway Station to Cypher Street behind the Boston Convention & Exhibition Center.

The work will include an electrified third rail along Track 61 to power the Red Line cars, a new shed, and other improvements. The testing will start at the end of 2018 and run through 2023, MBTA spokesman Joe Pesaturo said.

But the return of trains to the waterfront has raised hopes among some advocates that Track 61 will eventually be used to address the Seaport’s increasing traffic congestion.

“You’re keeping that rail line alive as a rail line,” said Kathy Abbott, chief executive of Boston Harbor Now. “Everybody understands and appreciates that there’s a need for new transportation options for that new corner of the world. This small piece of rail could provide an answer, in some form.”

Originally a freight line that was part of the industrial rail yards along the South Boston Waterfront, Track 61 has been unused for many years while around it a new neighborhood of glass-walled offices, luxury condos, and hip restaurants has sprung up. Representative Nick Collins, a South Boston Democrat, said he hopes the Massachusetts Convention Center Authority and private landowners along the track will help pay for improvements that will enable train service through the Seaport, all the way to the Raymond L. Flynn Marine Park.

“Moving people through the city is going to be more and more difficult as the city grows,” Collins said. “We need to get ahead of these transportation issues. Having rail, long-term, that continues to the waterfront, we think is critical.” The MBTA’s $32 million investment will start to pave the way for that.

Several factors complicate reviving Track 61 for passenger service. Governor Charlie Baker has been reluctant to embark on MBTA expansions until the state can solve the T’s persistent budget shortfalls. There aren’t specific projections on the cost of turning Track 61 into a passenger line, but such an endeavor would be likely to cost tens of millions of dollars, at least.

There is also a technical challenge: Traffic on Track 61 would have to navigate the spiderweb of rail lines in the Cabot Yard area, where the T services vehicles, without interfering with the existing traffic.

The type of vehicle that could carry passengers also remains up in the air. The Patrick administration had wanted to purchase self-powered train cars that run on diesel — like commuter rail train sets, but smaller and more flexible — for Track 61 and for the Fairmount Line.

But the Baker administration nixed that purchase in 2015, without pursuing another way to revive Track 61 for mass transit.

Transit advocates say the state should consider using electrified self-powered trains, known as electric multiple units, or EMUs, which are becoming much more common than their diesel counterparts.

The addition of an electrified third rail also raises the possibility that a traditional subway car, such as a Red Line car, could be considered.

Fort Point resident Steve Hollinger said the revival of Track 61 “probably opens the door” to some sort of reuse of the line. But he’s skeptical that passenger service on Track 61 could make a big dent in the Seaport’s public transit woes, particularly since the single track would limit the frequency of service between inbound and outbound trains.

“There’s only so much you can do with one track,” Hollinger said.

Richard Dimino, chief executive of A Better City a business group, pointed out that state transportation officials are conducting a comprehensive study of rail service within Route 128. Dimino said he expects the opportunities offered by Track 61 to play an important role in that analysis. The MBTA’s upcoming work on the track could help set the stage, he said.

“There are pieces of this that will be complementary to any future reuse of Track 61, and there are some pieces that may need to be modified as it relates to any future urban rail connection,” Dimino said.