However one possible legal argument is that the code submitter him- or herself is representing the code to be legally clear, and assumes responsibility in the event that it is not.
As SCO's code is not available for comparison, what expectation is there that IBM (for instance) would even be able to identify infringement? For that matter, what assurenaces does SCO have that Microsft (for instance) hasn't included some of SCO's intellectual property into their (closed-source) products?

If SCO would like to ensure their products aren't copied, they should file for patent protectin rather than pursuing copyright infringement claims. Then the code would be public, so other companies could compare new susbmissions for similarity, but still protected by the force of law. Or do they not think te ideas encapsulated in the code are original enough to be patented? Which would tend to shoot a hole in their entire argument that only be misappropriating their IP could Linux by where it is today.

And that, boys and girls, is called a Catch-22.