All research I've seen finds that talking while driving, even if it's just to a passenger increases accidents by a large amount. Other studies show that people tend to vastly overestimate their multitasking abilities.
So in short: very few people can actually talk safely while driving, and the people that think they can probably can't.
Most interestingly, it seems that people who think they're good multi-taskers are actually the worst at it[1]. They are more likely to be impulsive and more likely to indulge in risk-taking.
Maybe. The study does show that people that multi-task a lot are bad at multi-tasking. But it says that they didn't find a significant correlation between perceived and actual ability, while also assuming a negative correlation in part of their write-up. They also found that most people rate themselves 'above average', but that's not surprising.
So in short: very few people can actually talk safely while driving, and the people that think they can probably can't.