There is a third-party tool called Eshuttle from CompuSven (now Stellar Technologies) that can be used to do this. However, due to the complexities of this type of migration, it is highly recommended that you purchase some Scalix Deployment Services time.
Are you referring to locally saved nsf files? I don't believe it can do that as their website (http://www.compusven.com/) lists it as N/A. Regarding Scalix archives, yes, Outlook users can move messages into a local PST file.