Can you be more specific about what it is you want to preserve? Is it track effects applied in the Mixer? If so, those can't be copied and pasted--it's a tedious process of rebuilding. Track keyframes don't copy and paste either (clip keyframes do).
Here's a potential solution though: simply replace the original audio clip with the new one. I'd suggest duplicating your sequence first, and then drag the new audio clip to the sequence, position the clip over the original audio clip, hold down Alt, and release the mouse button. This will perform a replacement, maintaining the original mix. You can also use Alt+Shift to do a match frame replacement, which would be good if you've edited the duration of the source clip in the sequence. In either case, you won't have to do much to tweak the mix; this is assuming, of course, that the music is the same duration, etc.
I did a complicated mix on one long background music track and was not looking forward to doing that remix because of various minor music changes made by the musician scattered throughout that long track.
Your Alt (for replace solution) worked perfectly and saved me a ton of time.
The fact that Copy attributes for Audio doesn't work for copying audio keyframes is another reason do do audio mixes using the Mixer instead of using keyframes to adjust volume.
P.S. And a big LIKE to Adobe's clever programmers for including features like these.