These are a 'remnant' on Devos IV - ie they are not there in sufficient numbers to form an army faction themselves, they are an add on to the Loyalist IG.
Troops: HQ section (FW ones - woo hoo), two standard squads, two special weapon teams (snipers)
Fast Attack: a troop of three HALO warthogs (count as salamanders)
I'm seriously considering adding more squads, purely because the FW Cadians are so kool. But that is a double whammy because once you have bought the FW bits, you need the regular Cadian bods to complete them.