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?
Exactly like seen in here is not super common, in my experience. Usually in this situation the left lane would end instead of both lanes merging into 1. That is shown by the dotted line continuing until the end.
When two lanes merge, it tends to be at a narrowing of both lanes fairly equally.