  We consider the reaction $e^- e^- \rightarrow W^- W^-$ mediated by possible
heavy neutrino exchange at future LINAC energies of $\sqrt{s}>> 2 m_W$. This
reaction is sensitive to CP phases of the neutrino mixing matrices, even at the
level of Born amplitudes. Certain integrated cross-sections are shown to have
the power to resolve the CP phases when the experimental configurations are
varied. Asymmetries sensitive to CP violation (involving initial QED phases)
for $e^- e^-$ and $e^+ e^+$ reactions are constructed and their consequences
considered.
