TB: a little quibble. On the book side, just Vito, Sonny, and Tom meet Sol. Sonny tells Michael about it in a private conversation. So I don't think we know what the capos know about the meeting.
You're right, Pete.

Interesting that Fredo wasn't at the meeting.
Sonny, after the shooting, did tell Michael that he shot his mouth off. I've posted in the GF Trilogy board that Sol probably would have attempted to kill Vito even if Sonny had kept quiet.