1 its 2.4 gigahertz
2 cellphone towers would interfere with the 2.4 gigahertz controllers faster(which it shouldn't at all seeing they work on different bands) than the 27mhzAM, and 75mhz FM radios.
things that interfere with 27mhz are CB radios, cheap toy grade RC's are being used nearby that are not tuned very well, background radiation, bad crystals, poor batteries, etc