I believe Nomad players from the K'Hara or Das Wilde/Aoi Iseijin will be able to answer this better than me...
Though, from what i know - Nomads have no interest in Gallia, since it's not actually part of Sirius, hence they won't expand there. On the other hand though, there was an event, Fallen Grace, (which i'm not sure if is still valid) where the nomads did manage to infect Gallia, including the King - and some rebels along with other factions attempted to kill him.