TomTom or Garmin wouldn't help Apple that much. Garmin and TomTom both license either Teleatlas or Navteq for road data and they don't have access to much else since most of their devices are "offline" devices. Google has used Google Maps to build up a lot of data (they currently provide their own traffic on Google maps by curating all the data from mobile GMaps users, etc). A lot of people are missing out on the fact that "maps" that people expect today is a lot more than just road data. Getting access to road data is not that complicated for Apple to obtain. The rest is very complicated. Currently Google is the leader in this and there really isn't a close second (although Bing is doing some innovative things in this area).