That wasn't an IQ test. It was a direct test of firefighting knowledge. While the test was never released to the public, a couple of questions were.
They were mostly stuff like: "You are entering a burning factory which appears to be made primarily out of concrete. What sort of saw blade do you attach to your buzzsaws? a) Steel b) diamond coated steel c)..."
The court ruled that the test results should have been applied simply because the de-facto procedure of:
1) Promote people based on a test, BUT
2) If black people don't do well, ignore the test.
was racist in favor of blacks.
(Another question famously related to NYC geography, since the test was lazily copied from NYC.)