So, as far as I can tell, there is no capability to send Midi CC when changing a part.
Likewise there is no ability to change a part via midi.
Unless anyone can tell me otherwise?
If it doesn’t exist, this should be implmented to allow correct synchronisation fo multiple Octatracks, and proper midi control…
I’d say buckly’s and none.
Logged with support…
Feature Request:
Parts should be able to send / receive Midi CC messages.
Problem:
Not possible to change Parts remotely; and thus cannot have perfect synchronization of multiple Octatracks as no way to change Parts simultaneously.
Solution:
Suggest using Midi Continuous Controller message [ $3E 62 ] with values [ 0 = Part 1 … 3 = Part 4 ] to send/receive when Parts change.
This would allow synchronization, or extend the capabilities of the Octatrack when used as a voice module; particularly in light of the recent OSv1.40 update and Midi Slices.
Additional: Add option in the Project, or Personalize to enable/disable this behaviour via a boolean flag.
Aha. I was pretty sure it was your last misterious request!
Only one of many 
It’s one of reasons I prefer to change bank, rather than change part. It implies a part change, but it’s simpler.
I’d prefer a complete part feature, 128 or 256 available ones rather than 4 per bank that warps my head like the 8 voices of the 12 tracks of AR.
If I’d want a complicated set on a single project with many songs for live conditions, I’d probably change my mind, but today I don’t care, even for a live set I’d play ukulele or something during project load! 
Use Case #1: Two Octatracks Master/Slave synced.
Initial State:
Change to Part 02 on the Master, result:
New State:
So now they are out of sync.
Use Case #2: Octatrack as a voice module
Using the Octatrack as a voice module trigger samples/slices whatever.
Imagine being able to change the part remotely to access a new array of samples and associated fx etc?