I received information this morning that confirms the ability to amend prior returns that are still within the statute of limitation for receiving refunds. It was a 4 page document and there are many caveats to the right to amend prior.
In my case, the client was issued an ITIN in 2006, so he was filing legally. It is not a simple yes and no answer, just the same as most IRS issues.
There are caveats concerning prior actions, legally working in the US, etc., so do not take this as a direct yes.