[vikjon0]

In
/usr/share/skin/PM3.HD/720p/DialogButtonMenu.xml

<control type="button" id="13">
<description>Exit xbmc</description>
<width>80</width>
<height>81</height>
<texturefocus>sub-exit-focus.gif</texturefocus>
<texturenofocus>sub-exit-nofocus.png</texturenofocus>
<onclick>dialog.close(all,true)</onclick>
<onclick>XBMC.Quit()</onclick>
<pulseonselect>no</pulseonselect>
<font>-</font>
<label>$LOCALIZE[13012] XBMC</label>
</control>

I have not verified that this is the shutdown menu, but it looks like it is possible to find and edit the different menus.