When I see one trailer device like this, I always ask my self "what's inside ? how it look ?", and for those days, I seems to be lucky to found some answers ! this trailer is 83M6E2, one part of S-300 favorite complex(if I'm right !).
in public Almaz brochure it look inside like that:
As a work place, and it's really nice illuminated work place, it look like that, first level "what's inside ?":
And for second level deeper for "what's inside ?", (and really lucky found !), you see this: