Depends on the place -- at least where I've worked around here, lunch breaks have largely coincided with either individual preference, and the proximity to nearby (fairly quick) eateries.
If you're in a part of town, for example, where it takes a 10 minute metro ride to get to the nearest restaurant, it seems illogical to enforce a half hour lunch.
If you're in a part of town, for example, where it takes a 10 minute metro ride to get to the nearest restaurant, it seems illogical to enforce a half hour lunch.