It's important to note that as of yet no specific titles have been confirmed, though it appears we'll be getting seperate announcements on those in the near future. Whether or not "several months" of collaboration is enough for Rockstar to have been using this, after all there are only 10 months until the release of the game, it should be very interesting to see this technology used. This paragraph of text should help to explain why this is quite exciting news:
Oxford, UK-Feb 27 2007- NaturalMotion today announced a partnership with Rockstar Games, Inc., the world-renowned publishing label, to integrate NaturalMotion's revolutionary euphoria engine into upcoming next-generation Rockstar Games titles. Rockstar's integration of euphoria is well advanced, with today's announcement following several months of close collaboration between the two companies.
Announcements regarding specific titles will follow at a later date.
So essentially, you shouldn't see the same movements twice from characters, it will always be different just like in real life. It would certainly make for some very interesting game experiences. We may also see this technology used in some of Rockstar's other upcoming games such as LA Noire.
Based on NaturalMotion's DMS technology, euphoria uses the processing power of PlayStation 3 and Xbox 360 to simulate the human body and motor nervous system, thus creating fully interactive game characters that act differently every time. With euphoria, games move away from canned animation, towards a much richer, life-like experience that is unique to the player.
Press Release (pdf)