Oli, I think my namesake, not Fredo, tipped off Geary. In the Geary/Michael confrontation at Anthony's party, after Geary tells Michael that his move on the Tropigala will have the problem of the license being in Klingman's name, Michael's immediate reply is, "Turnbull's a good man." Geary's last words to Michael, after insulting him, were:: "From now on you deal with Turnbull."
What was Turnbull's source?