Airports don't choose c-in systems, airlines do.
There are many out there, Altea, E-Res, Skyport, Damerel, BABS etc.
Each airline will use whatever they prefer.
Some handling agents also have links with certain systems (Servisai and CODECO were very hand in hand) so if a carrier didn't want to go the the expense of installing their own they would just use the generic one of the handler at a cost of course)