The MTA confirmed on Wednesday that L-train repair work endorsed by Gov. Cuomo will cause serious disruptions — undermining the agency’s denials that had been exposed in Streetsblog’s earlier scoop.

The city and MTA will nix the inter-borough shuttle buses and surface-level improvements such as the 14th Street busway and Williamsburg Bridge HOV3 restriction that had been created for the now-scrubbed 15-month complete shutdown. The L train will keep running all day and night between Manhattan and Brooklyn — as the governor demanded — but service will be greatly diminished on weeknight and weekends as the MTA works to repair Hurricane Sandy damage in the Canarsie tunnel.

On weeknights, service between Manhattan and Brooklyn will begin to slow just after the evening rush, at 8 p.m. Headways will grow to every 20 minutes after 10 p.m. — the current arrangement between 1:30 and 5 a.m. Weekend service will be significantly diminished, with 20 minute headways — up from as little as four minutes now. Trains east of Lorimer Street in Brooklyn will run with 10-minute headways all weekend and after 8 p.m. on weeknights. There will be additional service on the G train, but the train lengths will not be expanded.

MTA Managing Director Ronnie Hakim told reporters that the agency is currently convinced that more night-and-weekend mitigation isn’t necessary because other subway lines will be sufficient to replace enough L train trips. But the MTA may change the plan after upcoming public meetings.

“This is not a final plan. This is the evolving proposal,” Hakim said, adding later, “We’re going to look to see just what is the demand. Our theme for our customers has been: If the L doesn’t work for you, please find other subway service.”

Only one bus service improvement is certain: Hakim said 14th Street buses will run every three minutes on weekends, up from the current range of four-and-a-half minutes to seven-and-a-half minutes between buses. But the previously planned dedicated busway is no longer in the works, and the launch of M14 Select Bus Service, originally scheduled for April, has been delayed.

The MTA may add more nighttime bus service on 14th Street, but will not be providing shuttle buses between the boroughs.

“At this point, we don’t anticipate closing 14th Street to vehicles, but we do anticipate working with NYPD in making our bus lanes … work as efficiently as possible,” Hakim told reporters.

Hakim did not confirm whether stations at First and Third avenue will become “exit-only” due to large crowds that are expected to gather on the platforms because of the extended headways. She said only that the MTA “may” make those stations exit only.

To avoid crowding at and around the Bedford Avenue station, the MTA may provide shuttle bus service linking the Bedford Avenue L stop; the Lorimer/Metropolitan stop on the L and G; and the Marcy Avenue station on the J and M lines.

Wednesday’s announcement matches up more or less with documents leaked to Streetsblog and Gothamist three weeks ago. At the time, transit officials claimed Streetsblog’s reporting was “irresponsible” because it was based on “draft and outdated reports.” The agency claimed the story did a “disservice to New Yorkers and our customers who need reliable, official information.” Then the MTA failed to invite Streetsblog to the conference call that basically confirmed the very reporting that it had publicly disputed.

Tunnel repairs will begin at the end of April, as previously planned. The MTA has yet to determine how long those repairs will take. L train ridership remains high well into the night and early morning. Huge headways are likely to result in severe over-crowding, which may cause wealthier riders to opt for for-hire vehicles.

The MTA could not provide any information on potential negative impacts on surface-level traffic. Activists blasted the news.

“It is all of the impact of the full shutdown with none of the alternatives,” said Transportation Alternatives North Brooklyn Chairman Philip Leff, whose group spent three years advocating for effective service mitigations. “This is a catastrophe for North Brooklyn. This just further extends the extent of the disruption, and is a complete lack of recognition that many people work in an economy that is not 9 to 5 on a Friday.”

Transportation Alternatives was more succinct.

“Mayor de Blasio’s new plan on 14th Street could be summarized in one sentence: ‘City to bus riders: drop dead,’” the group’s advocacy director Tom DeVito said.

“The MTA is right to run buses as frequently as every three minutes along 14th Street when L train service is severely reduced,” he added. “But these buses will plod along at walking speed if they’re forced to share 14th Street with space-hogging cars. Currently the M14 bus, which runs along 14th Street in mixed traffic, is among the slowest in the whole city, traveling at an average speed of 4 mph.”

Update (5:31 p.m.): In a statement provided to Streetsblog, de Blasio spokesperson Eric Phillips said the future of the 14th Street busway, HOV3 restrictions, and other street redesigns tied to the L-train shutdown is as-yet-undetermined.

“The Mayor hasn’t decided what to do with the city-controlled mitigation plans on the bridge and on 14th Street,” Phillips said. “As we learn more and more detail every day from the MTA about its closure of the L train, we’ll continue to design efforts and review existing plans to help affected riders.”