Someone mentioned geofence warrants, i.e. cops/feds asking "Hey Google, tell us which accounts had devices found in these time-space coordinates!", I guess they'd be asking mobile providers to do more logging as an alternative.

A Google account is probably more useful than a SIM card, which might be anonymous or have exchanged hands from the registered buyers, if you as a cop can ask Google to hand over the emails or IPs used by this account, you can find the person's identity and address (if using home IPs subpoena-able by asking the ISP).

I wonder if it's not just American police, imagine this question being asked by Russian FSB, or the "good guys" in the form of the Israeli authorities.

The cell providers actually do erase this data. I tried to subpoena it for a murder suspect to help show he wasn't at the scene, but he left it too late, and Verizon said that they delete their data after 5 years. I don't know the timescales of the other networks.

Not to say that the NSA don't have it all backed up -- I'm sure they do -- but for warrant (i.e. legal process purposes) it probably has a shorter timespan than the Timeline data stuck on Google's infra.