Its up on Steam, dont know about gamersgate version:
-Wet surfaces during rain.
-Terramorphing terrain under the tracks and wheels, depending on the soil and moisture.
-Increase staffing departments in the fast combat.
-New mission: Roads.
-New mission: Night Fight.
-New mission: Rangefinder.
-Added damage model for aircrafts and helicopters.
-Ability to rise up in the stowed position (M60 tank commander [Y]).
-Added achivs for passing certain single player missions.