The moment I saw the truck I thought it has Mars written all over it. Not simply due to the space aged look but the shape is good for sticking to the ground in high wind, it's impact resistant which would be good for the rocks that no doubt get thrown around in a Martian dust storm, great...
Bio-Defence cabin or room or anything that houses a person would generally mean pressurised I'm sure.
Perhaps "partial defence" means as sealed as possible but not positive pressure.