The Scala Eclipse plugin page says: * Support for Eclipse plugin and OSGi development including hyperlinking to Scala source from plugin.xml and manifest files.
How does
Yes, it is possible. In fact, the Scala Eclipse plugin itself is written in Scala.
I've never created a Scala RCP app myself, but I'm guessing that what you need to do is create the project normally using your wizard of choice. Once the project is in your workspace, right-click and select "Add Scala Nature" (or something to that effect). The result will be a Scala project with all of the regular trappings of an RCP app. You should be able to use both Java and Scala within the project after these setup steps.