Disclaimer: I've done work both on side channel attacks and Android security previously.
I'd like to see navigation apps make use of this approach when then lose GNSS signals, like in a tunnel.
It's a relatively well studied topic:
As I understand it Americans have no consumer rights so your mobile carrier will happily sell you out.
Open source basebands NOW.
Tracking location with other sensors requires more permissions.
Maybe "How smartphones can track you, even when you turn GPS off"?
But also, these researchers apparently didn't have access to cell-tower location data. Or at least, it's not mentioned in the article.
AFAIK you can be located using cell towers both on the device side and the cell network side.
You can be located with WIFI too: if you have WIFI enabled and communicate the access point names to Google/Apple, your location can be discovered. WIFI AP locations collected beforehand (by something like the Google car or the phone itself) are matched with their known accurate position and the measured AP signal strengths.
And Bluetooth beacons can also be used for location. What else... the pictures you take with the camera and upload to a cloud storage can be used to locate you.
Having a functioning inertial navigation would be very useful for many purposes. For example, offline navigation without GPS (=longer battery life).