The only material susceptible to moisture in the assembly is the OSB itself, which is essentially on the interior of the thermal & moisture boundary. So as long as you don't put a highly vapor retardent material up as a finish (such as foil/vinyl wallpaper or heavy alkyd paints), the moisture content of the OSB tracks the average humidity in the room.
The above-grade bricks produce a very high moisture drive when the sun hits it, but if there's an air gap between the brick and the concrete masonry unit (CMU) blocks it wouldn't likely create an issue. If the CMU cores are hollow, same thing- the air gap creates a partial moisture barrier. At 2" XPS is fairly vapor retardent- more vapor retardent than the OSB, so even if the CMU were saturated, the OSB would still be able to pass the moisture into the room without loading up and getting moldy. But if the gaps become an air infilration point it's theoretically possible that enough humid summertime air moisture could come through and condense on the exterior side of the OSB in a cool air-conditioned space, but air sealing the seams with mastic would be enough.
If you're going to finish the interior with wallboard, stagger the seams of the wallboard with that of the OSB, and use only latex/acrylic-latex paints as an interior finish. Wallboard is fairly permeable to water vapor, and standard latex paints are semi-permeable, 5-10x more permeable than the XPS, which is what you want in order to keep both the OSB and wallboard facers dry and mold-free.