Please reread my post.
As far as using them as a valid form of identification to get a TIN, the only government reference you can find on the internet is a reference to a government report to Congress. Looking through the rules even in 2003 the MC still wasn't a legal form of ID in the US.
Bank of America was seeking illegal alien business then and they said they'd accept the MC, but no one made them do that and even in 2003 folks were digging up bank regulatory rules that prohibited the use of the MC. There were several Congressional hearings on the question ID standards in fact.
What BAC wasn't telling the illegal aliens was that when a bank gets seized by FDIC if you want to take advantage of FDIC insurance on your accounts you will still need to have a valid form of identification ~ and the MC isn't going to cut it.
We had several "runs on banks" in Northern Virginia over the last year where 100% of the folks lined up were Latinos. ICE could have done raids on those lines and picked up nothing but illegals ~ self-identified by their intense interest in pulling money out of the bank before they lost it.