Given their description of how the cell tower/hotspot data is used, it seems like deleting "this cache entirely when Location Services is turned off" is the opt-out you are looking for.
I wish people would stop saying this. Of course it's tracking data. There's nothing wrong with that. One of the phone's features is tracking your location so you don't get lost.
Personally I think Apple has overreacted. They just need to provide a configuration setting for the size of the cache, and more importantly not include it in backups. A cache is not important enough to back up. But as far as the size of the cache, the defaults sound sane enough.
Hell, I get a text message from Rogers the second I land in the US to let me know that roaming rates apply. The fact that I have a device that has to talk to another end point means that I can be tracked.
Apple is now collecting anonymous traffic data to build a crowd-sourced traffic database with the goal of providing iPhone users an improved traffic service in the next couple of years.
"Tracking" vs "traffic". [shrug]
But I'd still strongly prefer to be able to opt out. GPS still works to find location without this data, it's just slower. I should be allowed to take that hit, for the trade-off of not sending in data. As biafra says below:
Tracking data is only anonymous if it cannot be de-anonymized. Since I cannot check that this is not the case (with Apple, Google and Skyhook) I have doubts about the so called anonymity.