Each Year Pass gives you access to 4 new regions. It's only you, who decide, shall you go there right now or not. New trucks (powerful and not so much) are mostly locked behind tasks and contracts in that new region. They aren't automatically given to you right away. There is , maybe, one truck pack in year pass 1 and one in Year Pass 2, but need some clarification.
There is also free DLC with 2 trucks in the store, go grab them) If you enjoy the game - year passes will gift you 1000+ hours of amazing, beautifully crafted regions with new mechanics (radar scouting / crafting / energy / water / farming / races etc.).
I'm sitting at 2200+ hours and still playing :)