A bit strange request, but yes, maybe.
For some examples of how to be a SIP session with a server, see Twisted SIP Test Cases . After the SIP session is established, you will need UDP to blow up your audio packets.
In short, it will be mostly manual work with lots of code. However, it is very interesting! Be sure to post it on github when you work it out.
Again, most of the heavy lifting is already associated with some other libraries , so using twisted SIP modules may not be the best in this case. Instead, you can wrap external calls in a twisted reactor and still feel cool!