Lesson for IBMers and other people lacking knowledge or network skills, we've had private addressing for a while, and if IBM is going to toss every acquired network (and some are really nice) overboard and reassign anyway, why not start developing a migration plan today to private addressing? Again, the real reasons have nothing to do with cost and/or culture. Have everything to do with "it's too difficult for IBM" and "IBM is too lazy".
Remember, IBM is forcing acquired companies to use "the 9" so you have to renumber anyhow. IBM already knows how to glue foreign networks in during transition. No, your arguments as to "why" are not the real reasons. And I'll tell you right now that you'll never get a truthful answer from IBM. It's not part of their culture.
Also remember, while not IBM (thus unimportant low lifes to IBMers), many companies did the right thing and moved to private addressing and even returned their large land grab blocks... Sure, it meant that "culturally" those companies had to change. And IMHO, some culture change at IBM could be a really good thing.