Similar now. Apple licensed Skyhook initially, and has switched over to their own database. This location tech is also built into OS X and can be used to find a missing laptop if it's within range of WiFi.

This cache of information (WiFi, and Cell towers for 3G units) on the iOS devices is what lead to the locationgate stories last year. It was mostly overblown, and in the investigation, Apple revealed a bit more info. Specifically if you use Maps on a unit without 3G, and search for something on the map, it also downloads WiFi location info around the area you searched. This allows GPS like tracking when the device lacks an internet connection and real GPS chip. It's not as good, but can be better then nothing for a quick walk in a downtown environment in a foreign city.

Also neat, the iPhone will relay actual GPS information to the WiFi only iPads if the iPad tethers to the iPhone.