Sadly not holding my breath for this to happen in America. After they tracked those spring breaker cell phones with ease, I’m afraid human rights are already being trampled.
In hindsight, cellphone data should have augmented contact tracing rather than just sitting on the sidelines and drawing maps a week later. In my opinion there is a time and place to wield technological power when there is a collective need. Ethicists can argue where the line is drawn but an existential threat to 2% of the infected seems sufficient, especially given how fast a pandemic spreads.
This kind of opinion is predicated on a utilitarian ethical viewpoint. I.e., it's okay to do wrong to a small number of people if it benefits the overwhelming majority of people.
There are plenty of other ethical approaches, many of which would say that the upholding of certain rights is more important than any benefits gained from violating them.
It's not merely predicated on a utilitarian ethical viewpoint, it assumes that we've accurately accounted for costs of the options (eg, second and third order effects) when deciding rather than merely justifying our preferences with biased models.
Empirically, the second (biased models) happens considerably more often than the first (accurate accounting) -- to the point that even if you're a utilitarian, you have to admit it doesn't work in practice. You simply can't make the required benefit calculations for utilitarianism.
This is something businesses get wrong a lot: their numerical justification is actually a reflection of the biases of their staff, rather than an accurate accounting of the options.
The counterpoint to this is that you can't just wait forever before making a decision. At some point, you'll have to do with imprecise data, and for a pandemic that is developing very rapidly, you can't just sit back and do nothing (well you can, but then you have to make an argument for why this is a good option).
As to the point of whether utilitarianism is a good ethical framework... well, at least no non-consequentialist ethical framework has ever convinced me. A naïve reading of utilitarianism has its problems, of course, but those can be accounted for; but the classical Kantian conundrum of not being allowed to lie to a murderer seems silly to me. Plus saying "principles matter" has just as many problems as the utilitarian approach, as nobody will be able to agree on those principles.
Your edit is worth debating, though I doubt there's an easy way to settle the argument between ethical concerns and the efficacy of tracking at phone cell granularity. Most of what I've read in that regard didn't really indicate that particular technological capability makes more sense than an overall lockdown since it can hardly be called targeted.
For further context: The example you replied to references this data in the hands of advertisers, with extremely questionable claims about their pseudo anonymization. That just made your comment before the edit less sensible. I believe such a debate might make sense at the level of a government agency, private entities exchanging that data is just a ridiculous idea.
Contact tracing via technology doesn't have to be via phone towers or anything like that (I agree those have little value outside of the aggregate). Anonymous tracking solutions via bluetooth that are much more are actively being developed and have also been advocated for by people affiliated with the CCC (as well as epidemiologists).
If everything else in American politics and government execution worked smoothly and some extra cell phone tracking could have unwrinkled the last wrinkles, I'd maybe give your argument consideration.
As it currently stands, getting cell phone data would be like polishing the door knobs while your basement is flooded. There are bigger fish to fry, lower fruits to pick etc etc.
Edit: I should flesh this out a bit further.
In hindsight, cellphone data should have augmented contact tracing rather than just sitting on the sidelines and drawing maps a week later. In my opinion there is a time and place to wield technological power when there is a collective need. Ethicists can argue where the line is drawn but an existential threat to 2% of the infected seems sufficient, especially given how fast a pandemic spreads.