After debugging some really odd behavior, I finally got the SuperAudioBoard working with the Teensy Audio library!
The Audio library additions are in my fork of Paul's github repo here in the "SuperAudioBoard" branch. Keep in mind that the additions are still in a beta stage until they get added to the official library so some things might change (class names, etc).
There are a couple of example sketches in the SuperAudioBoard repo that I'm using to test out the library additions.
I haven't had a chance to test out all the control methods (volume, muting, etc), but the base setup is working well.
Edit: I forgot to mention that there is a slight gotcha when using the Teensy Audio Library with the SuperAudioBoard: the Audio library defines it's sample rate at 44.1kHz, and all Audio library objects use that as the sample rate, but the SuperAudioBoard operates in master mode, and doesn't support 44.1kHz. The closest sample rate the SAB can support is 48kHz, so all code that uses the SAB and the audio library needs to take the sample rate difference into account when setting or reading frequencies. Check out the example sketches for details.