To correct a misconception, Twilio works with a variety of carriers, including Level3 and Bandwidth.com. Much like Google Voice, we work with a plurality of vendors for redundancy, geographic coverage, etc..

Voxeo also works with Bandwidth.com. "Bandwidth.com shares Voxeo's 'All-IP' worldview and as a result is an important voice network partner for us." --Jonathan Taylor, Voxeo CEO

http://bandwidth.com/about/read/flexNetwork.html