I have done this. The original charge to my corporate CC was retained, and converted into a Travel Bank credit, which was then used in conjunction with a separate charge to my CC to issue a new ticket.
If you're not Mosaic, they will also charge you the change fee to do this, on top of the fare difference, which might push it into the not-worth-it column. It also took a good 30 minutes on the phone, it seemed to be a complicated set of transactions for their system.