The latest video from Grand Theft Auto: The Ballad of Gay Tony demonstrates the Base Jumping feature in multiplayer Free Mode:
"Use parachutes to take part in Multiplayer BASE Jumping throughout Liberty City. Find the 9 BASE jump marker locations scattered throughout the city in Free Mode and hit Right Button to warp you (and anyone else with you in Multiplayer) to the top of the building. Clean, successful and well-executed BASE skydiving jumps will be tracked by time and other statistics that you'll be able track and compare with Friends at Rockstar Games Social Club."
Additionally, the Multiplayer section on the official website has been updated to include new screenshots and information about the Race and GTA Race game modes.
Link: The Ballad of Gay Tony Multiplayer