It only takes a piece of metal at the bottom of the bike to trigger the lights. I think letting bikers decide for themselves spells trouble. The majority of bikers will be sensible about it but they have their share of chavs in the States.
Sometimes. There is a set on my commute that doesn't detect me, and i either have to sit and wait for a nice obliging car to join the queue, or see (and you CAN see, pretty much 200yds) if it is safe and decide to run through.
I think there are two sides to every story, and on this one it might just be that the cameras can't work out who the bikes are without our plate on the front, and so they don't want the stats of failed-to-find-the-jumper - solution? make it legal for them to jump.
Problem would be the insurance side - you would have to say that the biker would be automatically at fault, but the what-ifs about speeding cars, no lights and all sorts means it gets complicated.