There are lots of details left to hammer out. This is like an announcement that there will be a committee to commission a study to hire a contractor to change a light bulb. The process will likely take a while and may not complete at all.
Oh? Do you know details on how it's going to work? All I can find is the BRICS Pay site with a very high level overview. They're talking a big game, but as of now all that seems to be public is just talk.