Are we going to publish joint journal/conference paper if certain teams get top rank?
Per the information at New process for submission of manuscripts :
Finally, note that after consultation with arXiv administrators, submission manuscripts will be combined into a single challenge proceedings document which will be uploaded. All challenge manuscript authors will be listed as authors on the uploaded document. This ensures that all submitters have their manuscript available in a citable location on arXiv. Of course, submitters remain free to also independently submit and publish their work in other venues.