if you set the "DMTF Tones" to "Out-of-band" or "RFC 2833" it will work.
any other setting is not guaranteed to work and probably won't.
edit: (3:47pm PST) it seems to be reading the phone number but not the pin now. so... yeah.
FAQ38 does not include a mention of Sponsored Accounts.
I've seen this question come up every few weeks on the Support Board and I can't seem to find it in any of the existing FAQs. 131 doesn't mention…
Before I answered this support request, I tested a few things (as explained in my IC there). the_cynic