The background is largely up at my website ( link), albeit originally written up for WFRP first edition rules (before Dark Heresy came along). Those WFRP1 edition mechanics are no longer there save for some WFRP1 style stat blocks here and there, and I've kept meaning to update the mechanics side of it to match Dark Heresy - which is now in publishing limbo again, of course. Most of those mechanics were cut when Dark Heresy became available.
I'm watching to see if there's any sign of Cubicle 7 taking up the Dark Heresy license, or failing that, I'm thinking of converting those crunchy bits to Zweihander when/if a 40K-esque rules expansion for that comes out. There were 'Dark Astral' rules in the Zweihander early access rules, that effectively cover exactly that. They didn't make the released rulebook (cut for space, I think) but could well make it to an expansion book.