ICOT,
If we agree O.P. is a reshus harabim mdoraisa, what constitutes a “break”? Why is Queens (or even Nassau) not affected by O.P.? Brooklyn and Queens are both part of the same city. Why should the Brooklyn-Queens “border”, be considered any differently than say the difference between Flatbush and Crown Heights (insofar that O.P. would prevent an eiruv)?
These really are somewhat academic, as I think (for whatever technical reasons) Reb Moshe (and the Satmar Rebbe I believe) paskened an Eiruv wasn’t possible in Flatbush, Boro Park or Manhattan.