Will Thunderbolt Cinema displays work with Mini DisplayPort equipped macs? Is it possible to plug a Thunderbolt cinema display into a Mini DisplayPort-equipped Mac and have it work?  This question suggests that it's possible and that it's pretty much the same cable, but I don't see any explicit confirmation anywhere.
Plugs are the same, cables are not. The thunderbolt cables contain chips and firmware.

I haven't used the new Thunderbolt display, however I am aware of the following:

MiniDP Macbook -> MiniDP iMac 27: works fine.
Thunderbolt Macbook -> MiniDP iMac 27: works fine.
MiniDP Macbook -> Thunderbolt iMac 27: does not work
Thunberbolt Macbook -> Thunderbolt iMac 27: works fine.

This is in my experience and confirmed from various Apple KB articles. So I believe it's likely you won't be able to use the Thunderbolt display on a MiniDP machine, as that is certainly the case with the iMac 27" models.