Apart from a few of the production team, none of the DW crew actually went to New York
apart from the odd bulding shot the entire episode was filmed in Wales.
So the Dr and Martha are not in Central Park they are probably in a park in Cardiff
Sure the shots of the Statue of Liberty etc were shot there but Tennant and Freema were added digitally
Bit of a waste of money if you ask me
surely the bbc has plenty of NY footage and seeing as most of it was CGI altered the money would probably been best saved for one of those "expensive" planet set episodes that hurts the series budget so much.