I would guess that system would actually be very bad at mass surveillance. The radar system would be tuned to detect very small movements (the heartbeat), and reject clutter in the category of anything not moving and static (debris).

So in a wide area with lots of movement, it's ability to determine if something was a separate object or person, and interesting on top of that would be severely limited.

But this is just a SWAG.

By itself, yes. Coupled with other systems, it could potentially be very useful for its ability to determine person-ness of a given thing.