Sorry but I just couldn't listen to the presentation.
That said, from what I understand, a couple of things spring to mind....
Per energy from the motorway network: rather than lay solar panels under the road, would it not be better to just lay them on the embankments? I'd be surprised if either approach were economically feasible, but solar panels in the tarmac would surely be far more costly, and wear out sooner?
Per heating & de-icing: Surely any road surface already acts as a natural energy storage device, heating up in the daytime and cooling at night. If the Solar Roads are more effective at staying frost free, it may imply they are just better insulated, to avoid energy-loss into the road's foundations. So the same effect could be achieved through new construction techniques with a thermal insulation layer. Almost certainly not viable economically, but still cheaper than solar panels.
