  We study the behaviour of a Schelling-class system in which a fraction $f$ of
spatially-fixed switching agents is introduced. This new model allows for
multiple interpretations, including: (i) random, non-preferential allocation
(\textit{e.g.} by housing associations) of given, fixed sites in an open
residential system, and (ii) superimposition of social and spatial mobility in
a closed residential system.\\ We find that the presence of switching agents in
a segregative Schelling-type dynamics can lead to the emergence of intermediate
patterns (\textit{e.g.} mixture of patches, fuzzy interfaces) as the ones
described in Ref. 1. We also investigate different transitions between
segregated and mixed phases both at $f=0$ and along lines of increasing $f$,
where the nature of the transition changes.
