Oh nice, you got to this just before I could!
I think one of the really interesting things about this article that the journalist seemed to completely brush over, but which Chris Cox mentioned more explicitly on his YouTube Community Tab post linking to this article, was this:
After questions from Brisbane Times, an Energy and Public Works department spokesman said: “the advisory speed limit on Kurilpa Bridge is 10km/h as correctly painted on the bridge surface”.
Emphasis mine. Apparently, these speed limits are supposed to be advisory, not binding. One questions why they use the red circle sign and not the yellow square, but still, this is good to know. It should mean that Bob* and anyone else who has received a fine should be able to get the fines overturned quite easily.