The article said a "cell simulator" was perhaps used, but they are unsure. When I worked in this area 20 years ago that was called a fake base station, and there were even commercial products that anyone could buy. Then (in France) it was forbidden by law.

There are rumors that police still use them.

The article says that it does not enable connections, but instead that the base station requires IMSI from the phones.

I guess it would not be too hard for an entity with good connections to modify a device like this to become a fake base station: