  We re-examine the likelihood for alien civilizations to develop communication
technology on the basis of the general assumption that life elsewhere could
have a non-carbon chemical foundation. We particularized the discussion to a
complex silicon-based biochemistry in a nitrogen solvent, and elaborate on the
environment in which such a chemistry is feasible, and if so, on what scales.
More concretely, we determine the region outside the habitable zone where such
organisms can grow and flourish and after that we study how our findings impact
the recently derived upper limit on the fraction of living intelligent species
that develop communication technology $\langle \xi_{\rm biotec} \rangle$. We
also compare this new restriction on $\langle \xi_{\rm biotec} \rangle$ with
that resulting from the extension of the habitable zone to accommodate
subsurface exolife, originating in planets with subsurface (water) oceans.
