No. And I don't expect it will change any time soon.
We worked around this issue by generating the prompts in a 3rd party engine and saving them out as .WAV files. I wrote a simple web service where the input is text to convert and the output is URL to the finished audio.
-
Marc LaFleur
Tech Blog: http://weblogs.asp.net/mlafleur
OCS Blog: http://gotspeech.net/blogs/speakingfromtheedge
LinkedIn: http://www.linkedin.com/in/marclafleur