They haven't said, but it got a stealth update Sunday, which added the achievements in. The Pitt's stealth update happened a week and a half before release, if that's anything to gauge it by.
I hope Broken Steel provides more content than O:A or The Pitt. Anchorage is neat, but has no real replay value at all - but it does add a suit of power armor that never degrades. The Pitt is better, but is still really linear.