Do we get the new FB integration at all or that reserved for 10.8 only?
The Facebook integration in ML (10.8.2) shows up in System Preferences under Mail, Contacts and Calendars. It doesn't show up on my Lion (10.7.5) machine.
In the two screenshots I've attached, Facebook shows up as just another email service you can set up on Mountain Lion (right picture). On Lion, (left picture) it's not there. The easiest way to look for it (if it's there) is to go to system preferences, then type facebook in the search box.