Firing Deck 12 clarification

While models are embarked in a Trukk they can fire their weapons. Does this mean if I have a unit of tankbustas and burna boyz that I can select both units and fire ALL weapons? For example 4 flamers and 1 rocket from the burna boyz and 5 rockets from the tankbustas? How do you determine line of sight when embarked on the Trukk?

While models are embarked in a Trukk they can fire their weapons. Does this mean if I have a unit of tankbustas and burna boyz that I can select both units and fire ALL weapons? For example 4 flamers and 1 rocket from the burna boyz and 5 rockets from the tankbustas? How do you determine line of sight when embarked on the Trukk?