“And remember that those 600,000 had to be in ONE place during that day. That clearly would be the requisite condition. It is highly unlikely that even in Warsaw, ALL the population passed through one city fare during one day. Today, of course, it is more prevalent in the world’s largest cities and this is why in New York, London and others, the eiruv is problematic and relies upon other kulos.”
This is not true. The ONLY place in New York City that has 600,000 people in one day is Penn Station, which is indoors. And even that is misleading, because that is the passenger count: Most of those passengers actually are double counted because they arrive in the morning and return home in the evening. 600,000 people is an enormous number.