My point is that absent information that Google simply does not have no matter how creepy they get, there's literally no way they can identify such messages as spam - exactly the opposite in fact because probably 99.999% of such messages that they process are explicitly not spam.

The only way Google would have to identify that this message was not for you would be to get the subscriber information from AT&T and cross-reference it with name and address information they had for you - and even then most of the time they'd probably be wrong (e.g. if the email is coming to you but the account is actually in a family member's name).