Rob wrote:
If the cell sites are above aircraft, the presumed problems with the
current setup that are the reason for the current FCC ban on digital
cell-phone use during Part 91 flying would no longer be a factor,
right?

AFAIK, the FCC ban is specifically on the cellular 900 MHz band.
There's a separate FCC document on rules for the PCS band at 1.8 - 1.9
GHz and AIRC, there was no corresponding prohibition in the latter
document.