According to
www.wtc.com, Silverstein Properties is the developer. I couldn't find anything about the owners of the land.
If the government owns the land, I can see the separation of church and state. But if the government doesn't own the land, people can pitch a fit all they want, but it would technically be private property.
As for the "cross", isn't it just two beams that "survived" the attack that resemble the shape of a cross?
If so, people need to get their panties out of a twist, they're the original beams and should be someplace in the memorial.