TMR put this up on their Facebook asking who has to give way, but that's too easy. A much more complicated question is: what does the law say around indicating?
I've seen people say only blue must indicate, others say both must indicate, and yet others say neither must indicate. Which is correct?
There is a way to know, it’s called a zipper merge as defined in a link I posted elsewhere in this post. They are done to reduce congestion and I suspect at times, post hoc on roads where there isn’t enough space for a proper lane end/merge.