The wording is so poor, all that's left is to interpret. And without sections 125 and 126 referred to, that's impossible here (but please don't bother posting them).
Unfortunately, such laws are written so that a judge can make everyone guilty, if he/she wants. I interpret it as meaning no signal is required after having got into a designated turn lane, because at that point you aren't turning anymore, you are just following the lane that has a single directed purpose to it. In other words, what if there was a laneway or side street off of a long dedicated right turn lane? Same as why there is no reason to keep a right turn signal on, while on the complete journey from start to finish on an off ramp from the highway.