[quote=@Nerevarine]
<Snipped quote by Isotope>

Hmm, I'm curious. Could there be a trans-Pacific slave trade going on between The Great Han and Cascadia? It could be a nice way for the Great Han to get rid of Colonial peoples to complement their practice of mass deportation. You know, if Cascadia is in need of some Coolies for construction. 
[/quote]

It's possible, that said slavery in Cascadia is largely in the form of servants for the wealthy.  I can imagine nobles buying 'exotic' slaves to serve them in notable quantity but mass import of labor is unlikely.  Refugees from the plains have already swelled the population, there's hardly a need for more mouths to feed.