Yeah it is said after Thomas Lucchese died, and the Commission was not getting anywhere with Bonanno, that Gambino met a few times with Costello.
Frank Costello still had loyalty from some of the crews in the Genovese family, and still held with respect by other members throughout the country.

"I have this Nightmare. I'm on 5th avenue watching the St. Patrick's Day parade and I have a coronary and nine thousand cops march happily over my body." Chief Sidney Green