The accelerometer in most phones is accurate enough to detect individual footsteps. Phones also include a barometer that is sensitive enough to detect which floor of a building you are on. With dead reckoning based on accelerometers, calibrated by GPS, compass, WiFi, and barometric data, people can be located to within centimeters. Activity detection, mode of transport--ha, child's play!

If you run Android, turn off "high location accuracy". It uses all of these features.

One of the hardest problems, a few years back, to solve was getting data to determine which traffic lane you were in. It was to provide targeted ads on billboards, that through reflection, could show different ads to people in different lanes based on "external" searches such as browsing patterns. To my knowledge the problem was not solvable using wireless telco data.

I've got a bunch of the privacy stuff on my Android phone, and even when I use Google Maps while driving I'll ask "where's the nearest grocery store" and it will regularly think I'm hundreds of miles from where I am. I can't even figure out why. It once thought I was in the ocean.

To be clear, when I am asking this, the phone has access to my location data and everything else it asks for.

The telcos probably have enough raw data that with a bit of machine learning they could get most of that information.