Agree with the scepticism about the "rescued" women, of course it's possible and would be a good thing if true, but for modern slavery purposes (for this new law is the driver, to be sure) there are much more likely but less easy/visible places to look. Just the press release is almost simultaneous with the raid, so how would they know?
A similar series of raids in 2013 produced scathing accounts from the women involved, see the guardian or ECP article for more info.
Regarding immigration status, when they say illegal press will immediately assume that it means illegally entered immigrants, but my guess us that many will be in the country legally, but not supposed to be working.