It seems that drivers in BC generally have a big problem when it comes to merging. In this case let's say from two lanes to one. In the normal course of events merging shouldn't be any hassle at all - take turns, one from the left then one from the right - it all moves along nicely, and has a minimal effect on holding up traffic. Not in BC! Here it appears to be everyone for him/herself.
In a perfect world the reader would never have raised this issue. We would all be courteous to each other and take turns when we were presented with a situation where merging was required. All would proceed happily and no one would have to spend more time than the other waiting their turn.
In my travels, I rarely see a merge sign on BC's highways. More often than not, you see a sign indicating that the lane ends ahead, and in this case it is the responsibility of the driver in the lane that is ending to make a safe lane change in order to carry on. Of course, the courteous driver in the adjacent lane should realize this and adjust their speed to allow the other driver room to move in, but it is not required by law.
In the case of a sign that actually displays the word merge on it and both lanes merge into one rather than one lane ending, neither driver has right of way over the other. Both drivers must take care to accomodate each other as they move to take up positions to enter the single lane ahead. The RoadSense for Drivers manual does not contain specific information for this situation.
Remember that right of way is something granted, not something that a driver insists upon taking. Defensive driving often means making exceptions for the selfish or socially handicapped drivers among us in order to promote safety.