Enligt C-kanon talade Liliac (och Jabba) Basic.
Han bowed again. “Lord Jiliac,” he said, in Basic, “it is a privilege to meet you, Your Excellency. Your cousin Lord Tagta says that you are always in need of good pilots.”
“Pilot Solo”-Jiliac turned bulbous eyes layered in fat upon Han, and peered down at him with faint curiosity-
“do you speak and understand Huttese?” (Clearly, he spoke in Basic as he didn't know if Han understood Huttese)
“I understand it, Your Excellency. I do not speak it well enough to convey the beauty of the language, therefore it is not proper for me to attempt to utter it,” Han said earnestly.
...
Han bowed to the younger Hutt. “Greetings, Your Excellency.”
“Greetings, Captain Solo,” Jabba replied with a gracious wave of his small hand. “Your reputation precedes you.”
Jiliac held out his own hand. “Enough chitchat. The holocube, Captain?” “Certainly, Your Excellency.” Han produced it, handed it to Jiliac.
(src: Han Solo series Book 2 - The Hutt Gambit)
Observera att om du söker efter "Huttese" i bok ser du att det ofta nämns att Hutts talar i Huttese speciellt i olika situationer (inklusive Boba Fett). Därför förklarar bristen på sådan förtydligande här att jag antar att det var Basic.