For service bureaus, printers, magazine publishers and other pre-press providers who are unfamiliar with Scribus, the notes available in the Pre-Press and Scribus PDF from http://docs.scribus.net are meant to address your concerns.
Direct Link: http://docs.scribus.net/content/en/pdfs/pre-press.pdfThis is currently an updated working draft, but it has much relevant information on Scribus created PDFs. This will updated with more information and test results as we have more information on hand.
Moreover, members of the Scribus Team offer commercial support for printers, pre-press bureaus and other institutions who are implementing Scribus in their production. You can contact them at http://scribus.biz