Okay, I've added og:audio support to the trunk version of the code. It is looking at the normal WordPress "enclosure" metadata, which is how WordPress does normal podcasts. I cannot be sure this will work with PodPress, since PodPress might be doing something stupid and overriding the normal enclosure handling. Didn't check. Might work fine.
Anyway, trunk version has the code now:
Note: You will need to be running WordPress 3.3 to use the trunk version. It has a fair number of 3.3-only updates, and I haven't had time to try to make it backwards compatible yet.
Additional note: In my testing, when I liked a post with an audio metadata in it, the audio showed up fine in my FB Activity feed (even played right from there), but screwed up my normal profile display using the newer timeline stuff. I have no idea why. I suspect Chrome dev version being broken somehow, since it was inconsistent and weird.