It will be playable at the same time all across the world.
On November 11, Grand Theft Auto: The Trilogy - Definitive Edition will be released, giving the original three 3D entries in the series a thorough cleaning. Rockstar has yet to offer a substantial look at the remasters in action, aside from the announcement trailer and a slew of gifs published earlier today, and at this rate, they probably won't, because launch is just around the horizon.
Rockstar has set a definite release date, and it will happen at the same moment all around the world. This means that, unlike in the past, players in the southern hemisphere will not have early access to the new game.
On November 11, at 10 a.m. EST / 7 a.m. PST / 3 p.m. GMT, or 2 a.m. AEDT on November 12, Grand Theft Auto: The Trilogy will be released. This is true across all platforms, including the PC.
This re-release is more than just an up-res in case you weren't aware: Grove Street Games has been hired by Rockstar to port the games from RenderWare to Unreal Engine. The lighting has been improved, the character and vehicle models have been upgraded, and the control methods have been simplified for newer players. We won't know how much of the soundtrack has survived until the remake is released, which is by far the most perplexing component of the remake.