Research in Progress papers
I would give a research-in-progress paper the same format as a typical research paper (using a typical format such as introduction-methods-results-conclusion).  However, the content of some of the sections would be different.  Using this format as an example:


Introduction This would probably be similar to the introduction on your final paper, but it should also give a bit of context on the progress of the project, so the reader knows how far along it is.
Methods Depending on the progress of the project, talk about what have already done, what you plan to do, and/or any decisions that still have to be made about what methods to use.
Results If you have preliminary results that you are comfortable sharing, definitely include them.  However, "results" can also be about progress so far on the project. e.g. "We have successfully completed three out of the seven ice cream launches", "We have recruited fewer accordian players than expected, but so far the drop out rate has been only 2.7%", and so on.
Conclusions You might reach tentative conclusions based on preliminary results.  But more likely the "conclusions" should be reflection on the overall progress of the work, as well as lessons learned so far.  


For scope, use your judgment. As with any paper, the key is to make it tell a good, clear "story" that will be interesting to the audience.  Focusing on one aspect of the work, or giving a broad overview of the project, are both possible approaches.

Beyond this, refer to the call's specific guidelines.  The page or word limit is usually a good guideline to how much detail they are looking for.