MCESG and Security Forces Regiment are still two separately run programs with their own commands, unique schools, and unique MOS designators. As of right now they just stuff you in Security Forces if you flunk MSG school as an MSG contract option. If you got dropped from the MSG program, you still have to go through the Security Forces Regiment Basic Security Guard School, and likewise having graduated BSC doesn't mean you can rotate into an MSG tour....you would still have to go through the MCESG pipeline.