I agree with you that you are not anonymous to Google. That is easy enough to deal with. Stop using their services.
The bigger question is whether or not Google anonymizes your data before sharing it. Just because the data is all there does not mean that it is being shared.
While Google might provide data along the lines of, "Within the last 30 minutes, 5000 people have averaged 35mph over this 0.1 mile stretch of road" ... They are not going to provide a detailed list of who those 5000 people are, the last time they bought gas, the brand of car they drive, or what they ordered for lunch to any random person who wants that information.
Are you certain that the data is not being anonymized? In the case of traffic data, it is trivial to do technically. Just write a function to replace the unique ID (cell phone number, ESN, IMSI, whatever) with a random primary key and retain the rest of the data (position, speed, time, etc.)
Maybe they are breaking it up into two buckets. One is used by Google Now for personal consumption (daily route suggestions). The other goes into the public consumption data (traffic reports).