Don't all current cars have the same problems with particulate emissions from tire and brake dust? Its not like Prof Kelly is suggesting that electric cars raise this amount, they probably do a better job of controlling it with less random speeding and braking that humans are wont to do.
Its just another case of someone who had to make some speech during his 15 minutes in the spotlight, and decided to quibble to show off his knowledge instead of just giving strong support to a good initiative. If there was some magical way to get rid of these emissions, he would've complained about something else like the pollution caused at the point of electricity generation etc.
Of course, news outlets will seize such comments to indicate how this solution isn't good enough, and then probably other vested interests will cry about how its a great economic impact without much gain blah blah. If it results in the plan getting shelved or pared down, the same prof will then give interviews about how lamentable it was and not realize his own role in the media confusing the public.
Yes, of course the ideal condition is to have zero cars on the road for no pollution at all. But this is clearly not realistic. As for reducing the number of cars, he doesn't have any solutions to it other than standard snippets like 'we should improve public transport'. Public transport can progress orthogonally with emissions control, and is only tangentially related to improving technology for private vehicles.