I have the following line in my
gtk-key-theme-name = "Emacs"
And that works fine in Firefox and e.g. gnome-charachter-map if I use Gnome Classic to log in. Pressing ctrl-a in this text field sends the cursor to the start of the line as expected. If I use Mate installed from the 12.04 repository on mate-desktop.org then the emacs keybindings are not honored. Ctrl-a selects all text.
I think that the .gtkrc-2.0 file is read for some mate applications - mate-terminal seems to understand
gtk-keynav-wrap-around = 0, for example.