My understanding is that anyone can do it if they provide a validation study showing that the IQ test directly correlates to job performance and doesn't discriminate on other protected statuses. My understanding is also that the number of companies that have done this is as close to 0 as makes no odds.
No, it can discriminate on other protected statuses as long as you can prove that the test has a direct correlation to work performance. (Actually, the decisions require 'a strong basis in evidence' of 'business necessity', which you would demonstrate by showing a strong correlation.)
