Hard to say, but the Wikipedia article says that AMT doesn’t make the CPU vPro, VT-d/x, TXT, and AMT are all vPro technology, including all the security features. I don’t think it’s impossible that none of the CPU features are needed for AMT, and that it can run on any version of IME as long as you have a chipset that supports AMT.
My guess would be that the chipset and not the CPU decides if you can use AMT, but I also wouldn’t be surprised if they used the CPU ID as a “license key” to make sure you couldn’t use it without paying.