Diffusing the return is actually good for the radar. If all return goes in one direction and there happens to be no radar receivers in that direction, radar won

Diffusing the return is actually good for the radar. If all return goes in one direction and there happens to be no radar receivers in that direction, radar won't detect anything. With diffused return at least some of it is reaching the receivers. Cell tower signals have higher frequency than VHF, which makes position estimation easier. Cell towers will work for a few days even if power grid goes down. There are too many of them to take out individually. Nuclear blast has EMP powerful enough to burn them, but by that time you probably no longer need stealth. With access to baseband code in modern cell phones it might be possible to build distributed passive radar surreptitiously. There is enough processing power, exact time and location from GPS, and communication over LTE.