Police do need a warrant to place a GPS device on your vehicle.
Data continuity is a function of data point frequency [0]. If all public space (and some participating private space) is monitored, the practical difference between a GPS device and a retroactive dragnet system disappears.
You are correct that police do not require a warrant to follow someone around in public, but these systems aren't that, and in practice much closer to the GPS tracking, which does require a warrant. It's unclear without trying this further in court which this should qualify as.
IMO: If the system has seen me exit the public space outside my home, or work, or someone elses home, or a store, or whevever, the system knows where I am at all points in time, like a GPS, with very little exception.