Execute command on launch of custom Terminal Window in OSX10.5+
ExecutionString was changed to CommandString
Use it in the same way. When you do a Shell > Export Settings… it outputs a .terminal file. In my file it is located immediately after 

&lt;key&gt;BackgroundSettingsForInactiveWindows&lt;/key&gt;
&lt;true/&gt;
&lt;key&gt;CommandString&lt;/key&gt;
&lt;string&gt;/blah/blah/blah/blah.sh run&lt;/string&gt;


(MountainLion 10.8.5)

So then you would run the following command from terminal or a script…

open ~/Documents/blah.terminal