Nvm then, forgot about the BS motherboard manufacturer specific header. If Intel was serious about driving TB adoption, it'd put out a TB-to-PCIe bridge chip with all the necessary management built-in instead of requiring proprietary side-channel access to the chipset. (And that is made even more BS if claims that the GPIO is mainly used to coordinate switching IGP DisplayPort output over TB even when you don't have any TB-attached displays or an IGP happen to be true.)
Too bad nobody knows what the proprietary interface does. It would be funny if a PIC12 could be wired to it to fake whatever the cards need to work when you aren't using DP/IGP over TB.