I doubt there is any such real law that designates the bike lane as using the pedestrian signal instead of the car signal.
Whenever I'm in a bike lane I treat it the same as the adjacent car lane and cross when that traffic light goes green.
Only place I can think it'd even make sense to go with the pedestrial signal, is if its a badly designed bike lane thats in the right turning car lane, thus one might argue that you need a separate signal since you're crossing the right turning traffic.
But this kind of sitation is really a moot point since thats when you take the lane and get on the left edge to keep moving straight and let right turners around you.