Are we sure that it's always MP running his twitter and facebook, btw? The most recent post refers to an "interview with MP." As in, third person. Mike Portnoy doesn't refer to himself in the third person, as far as I'm aware. (Although that would make for some really funny interviews.) Could be that a webmaster or someone read the article, thought it was appropriate, and slapped it up there.
Still starting to wonder whether the break might've been a bit acrimonious, though. They're no longer following one another on twitter, nor are they facebook friends.