Blueworx Voice Response supports playing RFC2833 DTMFs using the <value> element by extending the tag to include a mode="dtmfplay" attribute, e.g.
<form id="playDTMFTest"> <block> <prompt> <value mode="dtmfplay" expr="'123456*7890a#BcD'"/> </prompt> </block> </form>
Note: This mode should only be used for value tags that are inside prompt tags. The behaviour of setting this mode outside of a prompt tag is undefined.