just a followup... JensDoe appears to be correct. Once I enabled the lock screen and activated it, the album art and track info appeared. Oddly enough, the track length didn't. Still, better than it was. No idea how JensDoe ever unraveled that workaround!
Came to the forums to search for this issue... I'm not getting any bluetooth info on my car radio. Nexus 4 Stock jellybean 4.3 Google play music works perfectly. I get the track name, album art, track length. Poweramp... nothing. (I'll try out the lock screen workaround mentioned in the post directly above later today and will report back with any results.)