Here is the grammar, copied from MSDN. I'm afraid the online help doesn't explain how this is supposed to work.
I am guessing (I know, bad idea) that a queue of tones will create a container full of results. If so, where is the container?
<grammar mode="dtmf" root="digit" version="1.0">
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2001/06/grammar
http://www.w3.org/TR/speech-grammar/grammar.xsd"
xmlns="http://www.w3.org/2001/06/grammar">
<rule id="digit">
<one-of>
<item> 0 </item>
<item> 1 </item>
<item> 2 </item>
<item> 3 </item>
<item> 4 </item>
<item> 5 </item>
<item> 6 </item>
<item> 7 </item>
<item> 8 </item>
<item> 9 </item>
</one-of>
</rule>
<rule id="pin" scope="public">
<one-of>
<item>
<item repeat="4"><ruleref uri="#digit" /></item>
#
</item>
<item>
* 9
</item>
</one-of>
</rule>
</grammar>