“I remain mystified as to how some people believe they have the right to violate both the laws of the city and state of New York as well as halacha.”
Regarding tashlich, I would suggest that some community leaders approach the owner and ask permission to use the lot for that purpose.
The Bronx Zoo keeps one of their pedestrian entrances open on the first day of Rosh Hashanah so that the Jews of the Bronx can walk to the Bronx River for tashlich. They probably figure that it is a good business practice; on Yom Tov afternoons many frum Jews can be found in the Zoo.