These (and apparently other) studies were started to research the strange phenomenon that all these anti-cell phone laws have been passed on the justification that they would improve safety, but the accident and fatality rates have not changed as a result of the laws being passed.
A) everyone is ignoring the law
B) cell phone use may not have been as much a factor as people thought.
In one of the links, they were reviewing the data from one of the early studies that showed that cell phone use was so horrible. They found that when the study was comparing "accident" days with "non-accident" days, they didn't account for the miles driven. If they changed the calculation to be by miles rather than by days, the rate of accidents with cell phone use was 1/5 the rate calculated in the original study, bringing it down to almost the accident rate for non-cell phone use.
In the other study, they did question people on their cell phone usage, and then had them drive the same route. They found that the people who reported high cell phone usage had many other driving habits that made them more likely to get into accidents (higher speeds +5mph, 2x more lane changes, etc), raising the question of if the cell phone use was the _cause_ of these people tending to have higher accident rates, or merely a _correlation_ with their other driving habits. This is just looking at the more extremes (use a phone frequently, and almost never use a phone), so it's hardly definitive either, but they are counterpoints to the "Cell phone usage is as bad as drunk driving" drumbeat that we ahve been hearing, so I thought I'd mention them.