Hi Daniel,
As you've discovered, BIAB doesn't allow sections of Realtracks to be copied and saved. This could be be done if the song was in Realband -- if you have BIAB for Windows.
If you want to save sections of a solo and stay working in BIAB, it's necessary to save the audio file in BIAB and then drop it into a DAW. From there, it's possible to use the DAW to copy the section(s) you want.
What I do when I hear something that appeals...
1. I freeze the track - that means that that Realtrack, i.e. the frozen one, will re-generate the same each time.
2. I remove panning and reverb for that track because I like to add those in my DAW.
3. Then I make a note of (a) what bars contain the solo I want to keep and (b) the Realtrack number.
4. Next I right-click on the Realtrack's name in the mixer and from the menu that appears, I select "Track Actions" and "Save track as wav file".
5. When I name the track, I use the format RealtrackNumber_bars_xx-yy.wav. For example, if I use RT 3221 and I want to keep bars 34-42, I'd save the file 3221_bars_34-42.wav. Doing it this way allows me to know where to look once the file is in my DAW because the information I want is in the name.
6. I can now load that wav file into my DAW and extract the bars that I want.
Hope this helps,
Noel