Ok, thanks for the clarification, here is what I have and tried:
Test Hardware:
iPhone 5/IOS 6.01
2010 4Rnr Limited/JBL
Test Steps:
1. Enabled bluetooth on iphone
2. Selected a random song in my playlist, played it for a moment, then stopped it. Terminated the ipod app.
3. Started truck / allowed bluetooth pairing to connect.
4. Selected "BT" in the audio menu and within moments, the song I was listening to resumed.
5. Turned truck off.
6. Disabled bluetooth on iphone.
7. Restarted truck.
8. Enabled bluetooth on iphone
8. Waited for the pairing to connect.
9. Again, Selected "BT" in the audio menu and within moments, the song I was listening to again resumed. The next song that played was the next in the playlist, as expected.
I repeated steps 2-9 (twice), in every case, the song I was listening to resumed and the next song in the list played as expected.
For the record, my headunit also displayed all metadata (song title, author, etc) without issue, and I was able to use my steering wheel controls to change songs.
I was unable to reproduce your issue.

I'm sorry to hear you're having issues, a quick search on apple's forums did reveal quite a few issues with bluetooth.
https://discussions.apple.com/thread/4318307?start=15&tstart=0
Good luck man.