Believe it or not, I wrote about it on my now permanently suspended Twitter account.

Here is a remnant from someone who replied at the time:

https://xcancel.com/kpcuk/status/601451439215353857

By the way: somewhat later we (thanks to a group effort) figured out it wasn't "just" Chrome as mentioned, and this basically led to the strong assumption there was some serious data sharing involved.

And yes that screenshot from this person is 100% real; my pins for example were sprinkled all across Brighton in the UK near places with Wifi access (I recently went on a city trip there at the time), and my home town in the Netherlands.

Tweets were geolocated, with a 'see tweets near me' page until about 14 years ago, so it's entirely feasible that at least some of that infrastructure has survived the feature being removed.