User blog comment:Damac1214/Zombies TranZit mode having details released from October 8th-11th, Zombies Gameplay Preview coming October 12th/@comment-4050621-20121008215056/@comment-66.75.48.85-20121008221306

Because the main mode of transportation on that map is a bus. Using the bus is also called using public transit. Get it? Also, the Z probably stands for Zombie.