Some unexpected Christmas 'gifts' for New Yorkers

His name isn't Scoodles Shea, Unser Fritz or Jack O'Hearts, but he could have walked out of a Damon Runyon Christmas story. Standing in crowded Rockefeller Center Plaza, Percy Ross, a Jewish millionaire from Minneapolis, has been passing out dollars to any and all who contribute to the Salvation Army. Whatever a passerby tosses in the kettle, Ross matches, dollar for dollar.

And there's truly a goodwill Runyon-like twist to the tale: When he was a child, Ross's poverty-stricken family was helped by the Salvation Army. And now , as he passes out silver dollars wrapped in plastic bags that made him a millionaire, he says with a smile: "Sharing is caring." He hopes to give out $10 ,000 during the holidays.

But this upbeat, slightly offbeat bit of news is not alone this Christmas season for New Yorkers. Like a sudden snow, the nation's biggest city has received plenty of good news in the past few days. And for the nation's biggest city, which seems to have more than its share of problems, this is as welcome to many as sleigh riding in Central Park is to a 10-year-old:

* Buses. It's a Greyhound, it's a charter bus -- no it's a "Metrobus." About a week after 637 new Grumman Corporation's "Flxible" buses were removed from service because of structural defects, nearly two dozen Metrobuses on loan from the nation's capital were in service here by Christmas Eve, with another 75 scheduled to hit the streets, after tuneups, by New Year's Day. These rented vehicles, of course, are not enough to eliminate the rider crunch, especially during the holidays, and are surfacing a little later than hoped for, but this "christmas present" makes bus riding a little easier for many as negotiations continue betwen Grumman and the city over the repairs.

* A Manhattan federal district court judge, finding "mismanagement" of the 1980 census, has ruled that the US Census Bureau has substantially "undercounted" populations in New York State, and especially in the city here. In his 38-page decision, Judge Henry F. Wecker said that even "conservative estimates" of the undercount were in the range of 517,000 to 650,000 for the city alone. His decision, which is likely to be appealed by the Census Bureau, may save the state two congressional seats and millions of dollars in federal aid that is proportioned according to population. A spokesman for Mayor Edward I Koch, now vacationing in Egypt, said city officials will continue to fight for the most accurte population count possible.

* Subways. Unexpectedly -- at least this soon -- another federal district court in Manhattan has awarded the city $72 million as a result of a suit filed two years ago against Pullman Inc. and Rockwell International charging these two subway component manufacturers ahd "oversold and underdesigned" their products. Some of the cars produced jointly by the manufacturers developed serious cracks, the city had alledged. The $72 million will be used to purchase a badly needed fleet of new subway cars, according to Richard Ravitch, chairman of the Metropolitan Transportation Authority, who hailed the court decision.

"All this good news certainly does pick up the end of this year," says Patricia Scott, Mayor Koch's assistant press secretary, "especially the census victory. It was a strong court decision and even though it looks like the Census Bureau will appeal, it looks as though we will win the last straw."