  Noninteracting insulating electronic states of matter can be classified
according to their symmetries in terms of topological invariants which can be
related to effective surface theories. These effective surface theories are in
turn topologically protected against the effects of disorder. Topological
crystalline insulators are, on the other hand, trivial in the sense of the
above classification but still possess surface modes. In this work we consider
an extension of the Bernevig-Hughes-Zhang model that describes a topological
crystalline insulator. We explicitly show that the surface properties of this
state can be as robust as in topologically nontrivial insulators, but only if
the $S_z$-component of the spin is conserved. However, in the presence of
Rashba spin-orbit coupling this protection vanishes and the surface states
localize, even if the crystalline symmetries are intact on average.
