OK I'm going to pitch in here and say categorically it doesn't work on either a Mac Pro or a Hack. Having tried various methods of getting it going and its currently a no go. I intend on looking into this further after the Easter break, but I wouldn't hold your breath for anything happening anytime quickly.
Just to save the questions this is where I am.
The card is booting with full resolution (EFI mode with Clover) to the Apple logo and the spinner and then crashes. As to what is currently causing that crash is unbeknown to me.
I will update as and when I have something to update with.