Doing anything except taking care with your driving impairs your concentation.

As the research was conducted by those with a vested interest in the prevention of accidents, they would be more interested in backing up their opposition to the use of mobile phones.

I think any "research" conducted by mobile phone makers/providers would be counter productive and likely to be greeted with howls of protest along with accusations of bias.

To be clear, I think those using a hand-held phone should be prosecuted and if it's subsequently found (after examination of the phone) that they made calls or texts while driving, they should face a lengthy ban.