A widely distributed Bluetooth monitoring network noting tims and places ... might ... be able to correlate secrets with other data (facial recognition, MAC, UUID, etc.,) to correlate individual with probable SARS-COV-2 exposure status.

An in-location tracking system, such as numerous proposed retail monitoring systems, among othe.

Given time and location, a low number of hits would likely be sufficient.

This would be expensive, but likely within reason for a motivated entity. Possibly by utilising (with or without cooperation) existing infrastructure and systems.