CELL towers should all by now be totally digital, due to the fact that I doubt if there is any analog cell phones still in use out there.
When the batteries goes dead, people gets new phones, doesn't replace the batteries, and at some point, the batteries are probably not produced anymore - hence the phones are rendered unusable.

The phones operate on a band somewhere between 869 and 913 MHz.

4 G towers do not even use a fiber optic link anymore, because it is too slow.
There is a antenna on top of the tower which sends the signal directly to a satellite in the sky.
So I would have to wonder what kind of tower you live beside?
What is radiating the analog signal, and at that harmonic.

When the signals were analog, I could listen to them with a old Bearcat scanner by listening below the cell frequency to the 1st or 2nd harmonic which was slightly below the cell towers frequency, but it was one conversation at a time on a specific frequency.