Speaker Christine Quinn, Mayor Bloomberg, Borough President Ruben Diaz, Sen. Gustavo Rivera and tenants celebrate the sale of the Milbank portfolio at a press conference yesterday. By JORDAN MOSS and JEANMARIE EVELLYIt was a rare scene for the transfer of a residential apartment building: Tenants, a new landlord and a variety of city elected officials, from the mayor on down, gathered Tuesday for a press conference that turned out to be a celebration.The now-infamous Bronx Milbank buildings, including one at 2264 Grand Avenue, were finally sold last week to a new landlord after months of local organizing and city involvement. Tenants, advocates and elected officials had fought to wrest the portfolio of 10 deeply troubled properties from irresponsible bankers and owners to a responsible party who could afford to make them livable again. Over 100 people showed up for the announcement of the sale at 3018 Heath Ave., where the building had brand new windows – the first of what tenants hope will be many improvements to come at this and the other Milbank properties.”We now have someone to communicate with – someone to hold accountable,” said one tenant, Twyla Rashid, who described conditions at her building as “devastating.”The one to hold accountable now is Steven Finkelstein, a Scarsdale-based landlord who purchased the mortgage and the deeds to the properties in a $28 million deal last week, and faces a mountain of some 4,000 housing code violations.As part of the deal, Finkelstein promised to start making serious and immediate repairs and will have to report back regularly to the Department of Housing Preservation and Development about the work he’s done. “Accountability, I have no problem with,” Finkelstein said, as he stood surrounded by reporters with notepads and cameras.