I'm using iMovie 7, so I can't verify whether or not this is applicable ... and I hope this addresses your question correctly ... but until there is a definitive way to redirect your imports away from iMovie - here's a possible workaround:
If when importing you are required to create a project ... then save the project to the Desktop then quit iMovie and Ctrl/Right-Click the project and select "Show Package Contents". In the Finder window that open, search around in the folders there for your movie then drag it to the Desktop, close the window and delete that project once you have checked that the imported movie plays properly.