And they got it without treading on the cab companies' property, how?

I don't know. Ask them.

Oh, but I can tell you: the Commission pushed it, despite protests and even lawsuits from the private cab owners (see Taxi & Limousine Commission v. Hassan El-Nahal).

I was just pointing out that this very story disproves your claim that "private property is holy ground upon which the public may not tread unless invited", since that's exactly what happened here, and so I don't see why couldn't Uber also be "convinced" to install the trackers.

Ah, in that case, you're right. We should absolutely require Uber to divulge similar information.