hajime, I'm sensing some confusion about GPS that's causing you trouble.
In terms of your phone, or any other GPS device, the GPS system itself (the satellites) doesn't "communicate" with your phone. It's entirely one-way -- down from space, not up. Your GPS device receives signals from the satellites (basically, the satellites broadcast "here's which satellite I am and here's the time on my atomic clock," and the rest is up to the GPS receiver). Your GPS unit is passive with regard to the US GPS system (or Glosnass, or the new European one).
Then there are the apps and links that, having information about where your unit and/or phone is located, can respond to that information by sending you more information about traffic, etc. This are entirely separate procedures. They have nothing to do with the GPS system beyond that fact that before they can do anything useful, they have to know what positioning data your GPS unit or phone has gotten.
I think you've gotten those two data system mixed up with each other. Specifically, when you write "Through the iPhone's internal GPS?" you're mixing up GPS location data (passive) with traffic information (ordinary cellular data traffic having nothing to do with the GPS system).