https://www.apple.com/newsroom/2011/04/27Apple-Q-A-on-Locati...
It is impossible that a unique device submits data about cell and wifi locations in an "anonymous" way aside from putting another party in between (a party that you'd have to trust), and that caveat is outrageously nonsensical to anyone with a hint of technical capability. But we trust that Apple is then mangling it up. Or do they?
And even if a cell phone does keep the same IP address for a long time, I'm confident that Apple is completely ignoring the IP address for each submission and taking only the encrypted location data. Apple has gone to great lengths to preserve privacy in so many other cases, it's outrageously nonsensical to accuse Apple of trying to match IP addresses with location data to identify individual devices (and besides, even if they did do that, all they'd know is the rough location history of some device, but nothing at all about what that device is or who owns it).
My guess is that they don't given that they have a setting in location services called "Wi-Fi networking". But this should definitely be investigated...
I'm a (mostly) happy [0] Apple customer. The lack of evidence that they are gathering all my bits makes me comfortable to use their products. I strongly feel we'd hear leaks about how they are saying one thing and doing another if they were. Employees of Apple aren't that loyal.
Yet here we are with Google and their "it's better to ask for forgiveness than permission" attitude.
[0] iOS 11 is bad. Just bad.