It already passed. Can you not read?
As far as proving it if the officer has reasonable suspicion that you were txting he can certainly ask for your phone. Its pretty obvious when somebody is doing it anyways.
Looks like it takes effect May 5th. I would imagine there will be a state wide ban soon.
http://www.dispatch.com/live/content/local_news/stories/2010/04/05/city-fights-one-driver-distraction-texting.html?sid=101