“Hallelujah!” exclaimed the man in the red ACORN t-shirt, with passion not normally heard at Mayor Bloomberg’s staid City Hall press conferences. But this was a special occasion. Bloomberg and Comptroller William Thompson announced Tuesday that they had agreed to take $130 million in revenues from Battery Park City and put it in a trust fund dedicated to building and preserving affordable housing. Their proposal would begin to fulfill a 1989 agreement by the Koch administration and Battery Park City Authority to devote $600 million in authority revenues to affordable housing development.

For now, the trust fund remains a proposal. The Battery Park City Authority must agree to the mayor and comptroller’s plan, and the authority is controlled by Governor Pataki. Thompson declared he was confident that Pataki would sign off on an agreement.

Affordable housing advocates hailed the proposal as a breakthrough. “It’s a bold move, it’s a practical move, and it is a move that’s badly needed,” said Bertha Lewis, executive director of the New York chapter of ACORN and a leading organizer of demonstrations calling for the creation of a trust fund. The new dollars would be spent at the city’s discretion, allowing housing officials to combine the dollars with other subsidies to make new housing available for homeless and other poor. Currently, the affordable housing under the mayor’s affordable housing initiatives is targeted at households earning up to about $31,000 for a family of four; some of the new housing would be for households earning less than $18,000.

Also on the agenda, said Housing Preservation and Development commissioner Shaun Donovan, is a land acquisition fund, giving the city the capacity to buy up underdeveloped real estate for future affordable housing development. And Donovan is keen to use some of the money to finance the acquisition and rehabilitation of buildings that are receiving government subsidies but falling into disrepair; already, HPD has helped responsible new owners take over four that have gone through federal auction, and Donovan expressed confidence that the city can work with the U.S. Department of Housing and Urban Development to help New York groups purchase more. “We’ve had more discussions about a comprehensive solution,” said Donovan. “I’ll be in Washington again this Thursday to discuss the details, so we are making progress.”

The deal leaves some Battery Park City revenues untapped. It’s also not a permanent commitment–for now, the deal would be on for the next four years. “I don’t know that we can bind future administrations,” said Bloomberg.

That leaves advocates to hold the city and Battery Park City Authority accountable. “We’ll have to be all over it,” said ACORN’s Jon Kest. “There’s no magic. We’ll have to keep doing what we’ve been doing.” What ACORN and other groups in the Housing Here & Now! coalition have been doing is meeting with the comptroller since last November to press the issue, then mounting demonstrations to put the heat on the mayor, including a large march on City Hall and an action where tenants “moved in” to Battery Park City, carrying suitcases.

Tuesday was no day off. Members of ACORN, Asian Americans for Equality, Mothers on the Move and other groups greeted the mayor with cheers in front of City Hall steps. “You kept the promise–keep it up!” they chanted.

“We are going to keep this promise,” vowed the mayor. But Candidate Bloomberg clearly also wanted something back from the diverse agglomeration of neighborhood activists.

“I like this kind of crowd,” said Bloomberg. “Come back!”