Indeed! I don't need to analyze and reverse engineer sensitivity formulas for games that use a common engine like Source or Unreal Engine 3.
What I do need to do though, is some checks to verify how FOV and Windows Pointer Speed settings affect the sensitivity (this varies even for games that use the same engine), and to gather some information regarding config files, acceleration settings and raw mouse input settings etc.
And some games have their own unique sensitivity algorithm even though they use a common engine, so I always need to do some verification before I add the games.