My first instinct was that atmospheric attenuation would be the biggest issue here. But some preliminary searches suggest that is not really the case.
Figure 4 from here
https://globaljournals.org/GJRE_Volume13/4-Propagation-Power... gives an attenuation of at most 0.2db for 3Ghz atmospheric attenuation (0.2db at an angle of 10 deg, 0.02db when a satellite is directly overhead.
This means that essentially, power loss from distance is the only real issue power-wise. Which could be compensated for with large enough directional antennas.
Next thing I'd be worried about is angular resolution. As I recall, lower wavelengths have more of an issue with diffraction. So it might be hard to design an antenna that is able to listen to a small enough area that you can distinguish individual devices.
Cause if you are getting a 100m resolution, that means receiving all BT transmissions in a 100m diameter circle. Doing that in a city would probably give to many overlapping signals to do anything with. It might be nice for tracking people in the wilderness though.
I have no idea how optimistic or pessimistic the 100m number is. I get the feeling that with phased array antenna's you could probably get higher resolutions that you'd think. I would guess it might be worth it if you want to trace signals out in the open (say, in middle-eastern deserts)