These can currently be accessed by adding an Attribute node and specifying one
of those three names. A Smoke/Fire node should be added at some point to make
this more convenient.
These values might change still before the release, in particular for flame the
meaning seems unclear, it's just values in the 0..1 range. This is useful for
color ramps, but it might be good if this was also available as temperature in
kelvin so it can be plugged into the blackbody node. But I couldn't figure out
from the smoke code if or how this corresponds to a physical unit.
Here's a (quite poor) example file for a fire + smoke setup:
http://www.pasteall.org/blend/27990
Brecht Van Lommel
691c4c17ad