Transparency is just a first step, but it is a powerful tool.
(From the "Method" part at the end of the full article : https://nrkbeta.no/2020/12/03/my-phone-was-spying-on-me-so-i... )
Contact tracing addresses that shortcoming of the current surveillance tech. Today, finding out that 2 cell phones have been in proximity requires computationally expensive analytics on the server side. With the apparently mandated requirement for contact tracing, edge devices ("your" phone) will simply detect proximate "ids" and send that to the servers and that trivializes the task of determining your "romantic affair, secret meetings, or embarrassing health issues".
No, you just have to use the right data structures. Quadtree is the obvious one if you have lat/long, or if you have cell history you can observe that e.g. the UK only has ~25,000 base stations, so you can just use them as buckets. It's probably too expensive to run on every ad load, but for targeted surveillance it's easy.
Contact tracing will go away middle of next year with the end of the pandemic. Although I wouldn't rule out its reactivation next time there's a SARS or bird flu breakout.