Ok, I found some. They are here: http://ff123.net/peacefulspecview.html
The whole site is pretty good for codec info. I tried the hearing test that was linked there. Interesting stuff.

http://ff123.net/

You can see in the wma graph where the dropouts start at 13khz, there are some spikes up to 15khz, but they would probably just sound like ringing to me. The lame graph is cut off at 16khz due to a lowpass, but there are fewer dropouts.

Sean