This might apply for stationary or slow moving vehicles. However it does not work when the cell phone moves at M.80. I know for a fact a GSM cell phone will not work in a jet at cruise speed and altitude even over an area with many cell phone towers in range. Just saying.
What MK is saying is that cellphones at altitude
work better when few or a single tower is in reach, because no frequency interference. There is plenty of evidence showing that cellphones work in airplanes at surpringly high altitudes. Work in the sense they register with the network not that they are useable.