I just started working in a city and have wondered about potlucks in the city... how do city folks handle potlucks? Do people take their potluck dishes on the train in those insulated carriers? That's probably why my office isn't planning one.

Sounds like your office needed a potluck coordinator. Most of the ones I've been to have someone assign (for example) A-H Desserts, I-P Salads/Sides, Q-Z Main Dish or whatever.

What they do is put up a list of what is needed for the potluck. People then decide that even though there are only 5 slots for desserts, they'll keep on adding their name to the list for desserts.