I can’t tell you were I’m working because I don’t know if this site is safe. But I’m working temporary in a country as a Spectrum Manager. Since years we have interference on the ATC Tower. The equipment they are using is very old (R862/R863).
Could it be that the interference is caused due to the use of this old equipment (not tempest capable, loss of power,….)?
I never experienced any issue near airport myself, but i suppose it is possible. Don’t you think the multiple radar & communication systems would possibly interfer with the GSM system ?
It’s worth a try to upgrade the BTS, or possibly add specific narrow band filters at the top of cabinet.
As I said, I have no experience with this, but I can feel your headache 🙂