Until we have drones smart enough to focus on a specific car (vs. a mostly identical model right next to it), the drones will still require human operators, which makes the process not far removed from an old-fashioned tail (similar to the mentioned beeper case).
Targets can be laser painted/marked by a drone or more usually a secondary source and followed by a drone on the specific signature. This is currently actively being done in several combat theatres.
It is highly likely to be already happening in the US, particularly along the borders and in federal investigations.
