Pretty sure this is incorrect, as I had an old DisplayPort Apple Display that I used with HDMI input, and from what I understand, the Thunderbolt displays also supported DisplayPort. Granted, the adapter was not cheap, but it did work.
The Thunderbolt displays do not work with Mini-DP connections despite sharing the same physical connector. The DisplayPort signals still need to be encapsulated in a true Thunderbolt connection, so they don't even work with pre-Thunderbolt (but still DisplayPort) Apple Macs.
The Thunderbolt displays use the same connector type as Mini Displayport, but only a Thunderbolt handshake turns them on. There's no power switch, so it doesn't work.
