The only remains of multiplayer can be found in the code:

00_54_00_0001:%s joined the Game!

00_54_00_0002:Reason : User close.

00_54_00_0003:Reason : Server full.

00_54_00_0004:Reason : Bad version.

00_54_00_0005:Reason : Bad password.

00_54_00_0006:Reason : Server lost.

00_54_00_0007:Reason : Server closed.

00_54_00_0008:Reason : High ping.

00_54_00_0009:Reason : Inactivity.

00_54_00_0010:You ran out of time.

00_54_00_0011:Reason : Wrong mission guid.

00_54_00_0012:%s left the game! %s

00_54_00_0013:!!! TEAM KILL !!! %s killed %s!

00_54_00_0014:%s killed %s!





Question: Will there be any multiplayer features in the future?

2k answer:Mafia II is a story-based experience and we focused on the single player, story-based gameplay. However, we will have leaderboard support in upcoming DLC.

Source: 2k forum