That feature, in its original form, has been gone for a while.
Today, in the course of trying to filter people by city I realized there was no obvious way to do it.
A few searches on Google and Facebook forums turned up nothing useful in terms of a workaround.
But then I noticed that you can, of course, still search friends by hometown and by your current city — where you live now.
So duh. If you want to find your Facebook friends by any city in the world, simply change your hometown and your current residence. Then search those two fields.
You’ll see all your FB friends who list that city listed as their hometown or current residence in their shared profile.
That was easy. Got any other good hacks?