As much as rav Moshe was the posek hador an eiruv is a community issue, and IF a local rav has the knowledge to matir an eiruv then there is no reason not to. It's easy to be machmir. To say that the BP eiruv is not valid simply because rav Moshe held its not valid is a gross over simplification. IINM rav menashe Klein holds it would work, and he held it would work even when rav Moshe said it couldn't work.