Regardless, most of their studies and findings are from 1997-2003..... now a days, a lot more people use cell phones, which also means more drivers are using more cell phones.... that and adding the fact that blue tooth and hands-free devices are more common today, especially in the last 3 years, those older statistics and studies are clearly out dated.
I'd rely on the more recent, originally posted study then a "Study" based on assumptions by "Experts" and vague use of statistics created 7+ years ago.
Why are studies invalidated because of their age, if they are exploring the same issue? Hands-free cell phones have been around since the early 90s (I had a boss with a pedastal/cradle for his motorola flip phone, which plugged into some speakers and a mic in the sun visor in 1991). Just because the number of people using them has increased, doesn't mean attention span studies into their use are invalid: the devices really haven't changed all that much.
I can add some anecdotal evidence to this by stating that two out of my three speeding tickets were when I was on a hands-free phone call. I always found that because the mic was mounted in the visor, my head was up and I could see the road, but I didn't pay as much attention to my speedometer et al or road signs. Now I know this is just my take, as someone who used a handsfree kit for 10 years or so, but is still just an individual case and not a large number as should be used in a study.