oXygen supports remote editing, using the FTP/SFTP and WebDAV protocols. The remote files can be added to the project and can be subject to XSLT and XSL-FO transformations.
The WebDAV access is implemented using the Slide package of the Apache Software Foundation. The FTP part is using passive access to the FTP servers. Make sure the server you are trying to connect to is supporting passive connections.
The FTP/SFTP/WebDAV capabilities have been extensively tested with various servers running on Windows (IIS), Mac OS X and Linux (Apache).
If you want to access a WebDAV repository across an insecure network oXygen allows you to load and save the documents using the HTTPS protocol (if the server understands this protocol) so that any data exchange with the WebDAV server is encrypted.