I don't think that Harris is very habitable yet. Cambridge should have taken most of them. The purpose of Cambridge was to be a breadbasket for Leeds, hence there were population limitation laws in place which prevented cities from being built on farmland soil. However, with the loss of Leeds, I don't think these were really necessary and refugees could have been moved there rather than to Sprague.
Though I might be underestimating the BMM's capacity to exploit the working class.