Say I have a vehicle squadron of 3 big trakks or 3 gunwagons (from forge world). Each is transporting a different unit. Each vehicle is allowed to ignore the other vehicles for line of sight purposes, but what of the emparked mobs? can the lootas in one of them ignore the vehicle with tankbustas in front of them? and another related question: if the loota gunwagon was assaulted would the tankustas, lootas and burnaboyz

(those in the 3rd wagon) all be able to fire overwatch/wall of death? could I choose to only overwatch with one of them, saving to 2 others for the other enemy unit assaulting them?
Thanks in advance