Should blueboard overlap at outside corners or stop flush with framing?
Corner bead is used on plaster work too, so run it the same way as you would drywall. My preference is to run one piece over the edge of the other side, but slightly behind. This can be achieved as well when the board is ran past the corner, then scored at the corner an broke back and finished cutting. Use a drywall rasp (cheese grater) to insure the break is back a little behind the corner if needed.