EDIT: Yes, you could wire roads only when already performing needed repairs. Yes, you could run wires above roads for power. But why? All of these miles we have of infrastructure, it'll be faster to continue to drive down the cost of battery technology to the point where people will say, "Can you believe we even considered wiring roads?".
My opinion is that battery technology is going to follow that same cost curve as solar modules: http://cloudfront.mediamatters.org/static/images/countyfair/...
Within 5-10 years the cost of battery technology should have fallen to where the cost of the battery is marginal. The trick is to get the cost of the cells down, while reducing the need for so much manual labor to assemble the packs from cells. My hope is that Tesla comes up with a way to automate pack assembly or 3D prints the entire pack, cells and all (perhaps not "print", but laser sinter).