The intention of Frankie getting off alive was evident int he 2nd draft of the script. I have a hard time imagining that the dynamics of the Pentangeli hit had changed from one revision to the next. The outline of the story is consistent throughout. Obviously things are trimmed here and there for brevity.

So I find myself believing that Aiello knows this portion of the script and came up with the idea of his line in order to make the new revision of the script make a certain amount of sense. Unfortunately, tagging Aiello's line as an ad-lib somehow renders the whole thing UNclear, rather than clearing it up. Such is the bane of the internet.

MICHAEL
How did they get their hands on
Pentangeli?

HAGEN
Roth engineered it, Michael. He
made Pentangeli think you hit him.
Deliberately letting him get off
alive. Then the New York detectives
turned Frankie over to the FBI. My
informants say he was half dead and
scared stiff -- talking out loud
that you had turned on him and
tried to kill him. Anyway, they
had him on possession, dealing in
heroin, murder one and a lot more.
There's no way we can get to him
and you've opened yourself to five
points of perjury.


I understand that this particular script is not canon while the film is. I don't consider it canon. But I do consider that this script validates and verifies particular motivations behind these scenes. So though the film may not say it, I understand the motivations behind it because of this earlier script.