Vincent Massol has held an internal training at XWiki SAS about the Development Practices used by the XWiki SAS product team in charge of developing the XWiki open source project (among other projects). Most of the practices detailed are those from the XWiki open source project, defined on the dev subwiki. However the slides also provide a glimpse of other development practices that are used to complement the open source practices, such as Roadmap preparation and Stakeholder meetings.
Note: If you wish to understand the relationship between the XWiki open source project and the XWiki SAS company, check out this FAQ entry.