Ask HN: To what ends might a contact tracing app be applied?

There is currently much concern over privacy issues in a contact tracing app, but so far the discussions I've read discuss the efficacy at the stated purpose as well as the more general privacy concerns.

What I have been wondering is how lawyers and ultimately governments may choose to exploit this data from the perspective of establishing causality.

For example, driver A leaves their county home and drives on a stretch of road that has a posted speed limit of 35 mph, but travels at 15 mph behind a bicyclist before reaching a legal passing zone.

Later in the journey, driver A passes a driveway immediately before driver B pulls out of the driveway.

For the duration of the trip, driver A is unhindered by traffic and driver B is behind driver A.

Driver A stops at a stoplight with the intent to drive straight through the stoplight. Driver B stops behind driver A but will be turning right.

No cars travel through the intersection prior to the light turning green.

Driver A drives straight through the intersection while driver B makes a right turn behind driver A.

Tragically, a box truck runs the red light and comes speeding through the intersection striking driver B's vehicle in the driver's side door, killing driver B.

But for the bicyclist causing driver A to travel at 20 mph in the 35 mph zone, driver B would still be alive.

Does it seem implausible that this sort of scenario will be a result of contact tracing apps?

(Assume a "right on red" state)

How else might this technology be employed?