The first time you login to your town after updating the app, you'll see that the train is waiting with the picture of a person hovering on top of it. This traveler has a request for you, and you'll need to complete it before the train leaves to be rewarded. For instance, my very first request asked me to build a Suburban House in my town (or collect from one that's already present). Tapping on the train after accepting your goal (whatever that goal might contain) gives you the time limit for how long you have to complete the quest before the train leaves the station, taking the traveler and your potential prize along with it.
In keeping with my above example, after building a Suburban House in my town, I received 1,000 coins. Depending on the goal (and your own luck), you could win other prizes like even more coins (apparently up to 20,000 coins a goal) or boosts of up to 7 energy points. With the goal completed, the train will leave the station, and you'll again be able to tap on the station to see how long you'll need to wait for another train to arrive.
This is where the real-world time component comes into play, as a train will arrive on the top of the hour, seemingly ever hour of the day, so long as you continue to come back and deal with the train that arrives next. It seems possible to miss trains entirely, if you take a long break from playing the game, but you can always come back to receive more trains once you become a regular player again.
It should be noted that you won't gain any new land with this update, but you can manually expand out to the Train Station to make it seem more "included" in your town if you'd like. Either way, this is an interesting new update that at least gives you something to look forward to, if you can create a schedule of logging in that frequently to catch all incoming trains.
What do you think of this Train Station upgrade in CityVille Hometown? Have you received any awesome prizes for completing these train goals? Share your experiences with us in the comments!