Well, the ONRESUME command was doing nothing at all. It wasn't until I set hibernateaware=false. Then the ONRESUME command began working.
But now, I do not get audio from the HD or XM radios upon resume. If I restart RR, then it works fine. But lose audio upon the next resume. MP3s work fine.
But, the antenna up/down works fine now! That onresume command works.
EDIT: Should have mentioned that I can communicate with the HD or XM radios via the serial link. I get the name of the artist or signal strength (in XM). Just no audio.