Probably none, if they were never used. Again supporting the idea that they are better at creating a feeling of security than actually making any difference.

Maybe no emergencies occurred because of the presence of these emergency call stations. (At least those perpetrated by other people, i.e. assaults, thefts, etc.—I presume potential perpetrators would be discouraged by the presence of these call stations.)

Creating a feeling of security is as important as creating security—you need both.