I won't pretend to fully understand interoperability or how we will achieve it, but I do agree that it is necessary to achieve interoperability to integrate BIM into the industry.
My vision on interoperability is both simplistic and idealistic, but I think it makes sense. Instead of opening RVT files in Revit, DGN files in Microstation and SKP files in SketchUp, we should be able to open BIM files in all of them (much like how I can open a JPG in Paint, Photoshop and Windows Picture Viewer - among many programs). The objects for the building models would be PIM files (instead of RFA, etc. files).
Too simplistic? Perhaps, but we probably won't find out for quite some time because software companies don't think that it would be beneficial to have that level of interoperability. Consider the recent Autodesk lawsuit against the Open Design Alliance. Clearly, they aren't ready to "play nice" with any other company (despite the fact that most companies have the ability to export to DWG format).
Again, I don't claim to fully understand this situation. However, I think that a little cooperation from and collaboration between software companies might not be a bad thing.