  Shot noise cross-correlations in normal metal-superconductor-normal metal
structures are discussed at arbitrary interface transparencies using both the
scattering approach of Blonder, Tinkham and Klapwik and a microscopic Green's
function approach. Surprisingly, negative crossed conductance in such set-ups
[R. Melin and D. Feinberg, Phys. Rev. B 70, 174509 (2004)] does not preclude
the possibility of positive noise cross-correlations for almost transparent
contacts. We conclude with a phenomenological discussion of interactions in the
one dimensional leads connected to the superconductor, which induce sign
changes in the noise cross-correlations.
