Michael's "Turnbull is a good man" struck me not as sarcasm, but a reminde: "Hey, I thought I already took care of that through Turnbull, your bagman." So, "Turnbull is a good man" could have been a left-over reference in a different context involving an abandonded scene or story line. I thought it flowed well as a statement of surprise.
Yes... even if the "Turnbull is a good man" from another set of film scenes... it seems to fit. I agree that its an indirect way of saying "I took care of that with Turnbull already"...
And another way "never tell anyone outside the family what you are "REALLY" thinking" - it meant that I already paid... but he never says "I already paid for that"... so in a court of law... he could never be convicted
