A radar suitable for a small port or harbour is not particularly expensive. You can pick up a very nice complete system for ~$5k, a budget system is ~$2k.
Does this system cost less than that (I can't realistically see how), while providing coverage as good as a purpose built marine radar? What happens if your passive signal source goes down.
Have attended a few tech-focused talks from disaster relief people, I can't recall specific examples sadly. I only remember being surprised by the amount of time the first people to show up and help had to spend working under assumptions that needed to be made because of the complete lack of ability to communicate and coordinate. Very basic things like when and where helicopters/boats are going, and who has what. IIRC it was after a devastating tsunami
In the scenario you are describing (disaster relief) the simplest solution is to use what is already available. That would be the cheap radar set that you bought for the purpose of being a radar set for the port, or simply asking to have access to any of the dozens of existing radar sets already installed on most of the boats in port.
My point is that this uses additional hardware and an outside dependency (transmitting cell sites or other RF sources) to replace very affordable, ruggedized, reliable, safety-critical hardware that already exists. If your port control needs radar, the solution is to get a radar, not to pioneer a new technology that is almost as good as radar when it works correctly.