You are correct that you can use blocking volumes in a similar way. You can set the collision of your blocking volume for whatever you like; by default it will block rigid bodies.
Another option would be to export your BSPs as fbx files, then import them as static meshes (you can even keep the applied materials). If you set the origin point of the exported/imported BSPs to 0, 0, 0 it will place them back in the location they were exported from. This is just a work around until you can replace your objects with their final meshes. Please let me know if there is anything else that I can assist you with.
-Alexander