For anyone reading this thread in the future...
I just won my case two days ago based on this same scenario.
I was able to provide my cell phone records that showed no texting or browser activity.
I submitted R. v. Kazemi which challenges the word "holding" in 78.1 and that it should not be taken as literally as they are right now. It was a decision made at an appeals court which means it is binding and should influence a Justice of the Peace's decision in traffic court.
Look up this case on www.canlii.org
I also submitted R. v. Osman which is a case where the person claims to have been charged under the wrong subsection.\
All this being said, the Justice of the Peace decided to dismiss the case. I have to thank Kazemi for setting some precedence here.
It's ridiculous how they are just blindingly handing out these tickets. And people are made out to be guilty instead of proven innocent.
Feel free to PM me if you'd like to ask me any questions. I'm just a regular guy who Googled his way out of a texting ticket. I found alot of info along the way that made me fully understand the process of fighting tickets. Can't wait to help out my buddies in the future. I had a prosecutor that was taking his time in giving me the information I needed as part of my disclosure request. There's nothing like quoting him Section 7 of the Charter of Rights and Freedom to get what you want in a couple of hours... 
I'm hoping my case will help set precedence just like Kazemi's. It's time that lawmakers rewrite this law so that it makes more sense.