There are several public GSM/Cell databases[1], the largest of which are probably OpenCellID[2] and the Mozilla Location Service[3]. Their coordinate points are estimations from user observations, so the accuracy may leave something to be desired. Perhaps it could be combined with the OpenStreetMap database which has data for observable cell towers in places where contributors have added them. There are also a couple Android applications[4][5] that claim to detect IMSI-catchers, but I'm not sure what data they use or how publicly available their findings are. Either way, we are living in a golden age of sousveillance and great opportunity to use collaborative technological systems to increase transparency.
[1]https://en.wikipedia.org/wiki/Cell_ID [2]http://opencellid.org/ [3]https://location.services.mozilla.com/downloads [4]https://secupwn.github.io/Android-IMSI-Catcher-Detector/ [5]https://opensource.srlabs.de/projects/snoopsnitch