Seemly mostly no.
Someone was complaining here his 480 doesn't work with his mobo, and that there is no BIOS switch.
And on reddit someone posted a screenshot of Sapphire support system, where they already put their entire lineup in the list (when you select a product to create a ticket), all the new 400 series GPUs have written in parenthesis "UEFI" thus I assume even the custom cards are all UEFI only too.
And a minor nitpick: "AIB card" is redundant AIB actually means "Add In Board", even the reference card is a AIB. People are misusing a lot the term AIB because of the phrase "AIB Partner" (Add In Board Partner), that means non-AMD AIB manufacturer... but AMD make their own AIB too (engineering samples and some reference boards), and "AIB Partners" also make reference AIB, and custom AIB.
So in short: AIB means "card", thus AIB card means "card card".
Thanks for the aib clarification . I was hoping it would work so I could put off a major swap over for a while longer. I was curious because I have a g45 express chipset mobo non uefi of course that works perfectly well with a zotac 750ti which I think was told it was uefi.