Per Genlab Alpha, here are the official changes (that I could find) to Mutant: Year Zero rules not already added to the PDF version 2.
NPCs AND MUTATIONS At the start of each session, the GM gets a number of Mutation Points to her pool equal to the total number of MP that the players have combined.
Reflexes Mutation Fight or Shoot an enemy a second time in the same turn. The extra attack costs you 1 MP. You don’t get an extra maneuver. (E)
INITIATIVE ROLL Roll a D6 each. No skill is used, and you can’t push the roll. The one who rolls highest acts first. If it’s a tie, highest current Agility score goes first. If it’s still a tie, break it with any unmodified die roll.
GRAPPLING As a stunt when you Fight, you can choose to pin your opponent down using fangs and claws, or just your body weight. To break loose, your opponent needs to win an opposed roll for Fight against you. This roll counts as an action for your opponent but not for you. While pinned, your opponent can perform no other action requiring physical movement.
Grapple Attack: While grappling someone, the only physical action you can perform is a grapple attack against the opponent. This counts as a normal close combat attack, with these differences:
--You can’t use any weapon.
--You get a +2 modification.
--Your enemy cannot defend against the attack.
--Strength: A ration of food per point of Strength to be restored.
--Agility: A ration of water per point of Agility to be restored.