The LCC model is to operate with one common type, the A320 family being one type as far as crewing them are concerned, likewise the B737-6/7/8/9 family.
Harry Wayfarers,
The economics of the C Series operationally is attractive as we know, but more importantly the introductory pricing that is being mentioned in the media and by Boeing is such that the 'one common type' approach could be turned on its head commercially.
Swiss appears to be very happy with the C Series, and as a part of the Lufthansa group it is completely conceivable that the wider group could look at it. That said the LH groups seem to be a tad disjointed with fleets, e.g. Brussels Airlines does ACMI and LH itself has a bunch of types.