As a student pilot, I can tell you that yes, cell phones cause chirping in the pilot's headset. Ever leave your cell phone near your computer speaker as a call is coming in? It makes the same noise, only about 20 times louder.
If I leave my phone next to the CD player/Radio in my kitchen, it really screws up the AM reception. So I see what you mean.
Will they have to do something to the cockpit to keep that from happening when they start allowing cell phone use? Or will they install some sort of antenna to channel the cell signals to the ground?