K, this is the first time I noticed this but on the episode "Questionabal Ethics", the labs seem to be a bunch of holding cells for the aliens. Like they captured them when they first explored Xen (i.e., the survey team explained in Bshift). Maybe they were doing harsh experiments on them (hence the name for the episode). And maybe this is why the Xen enemies were hostile towards humans?. Anyway, thats sorta my theory...