Cities don't plant fruit trees because the fallen fruit makes a big mess, attracts rats, etc. Meanwhile, there are plenty of beggars in tropical places where unlimited fruit of all kinds grows everywhere...
Other problem is that this trees lose aesthetic value and health. This can sound silly, but good trees are expensive, and a mishappen tree that only have good flowers in the 50% and with stems that break or touch the soil by the load of the fruit in a narrow street will be chopped.
But if we think a little about it, to have fruit trees in suitable areas is common sense and an ancient culture of sharing that is lost now. Those trees were invaluable life-savers at war times in Europe, for example. The place for fruit trees is in a park, where you just don't care if there is some fruit around the tree, not in a narrow street.
As long as this guys be consistent cleaning under canopies, and prune low or broken stems, they will have much more possibilities of success.
Remember also that fruit in the street should not be treated unless you put a 'warning pesticides' signal somewhere.
I live on a street where grapes grow freely (as in, not on anyone's private property) and it's neat to see old ladies and birds pick at them. Yeah, a lot of the grapes end up on the ground but it's not a massive problem. In inner city areas you'll find people are already quite good at looking where they're going because the density of humans correlates with the number of dogs and thus the amount of dog shit everywhere.
It also correlates with the number of assholes not looking where they're going who will home-in on you like a heat-seeking missile when their eyes are affixed to the screen of their phone and plow into you if you don't take evasive maneuvers.
I for one welcome growing things of value in the city, not just lawns and decorative plants (which the animals - rabbits and deer here - eat anyway but people don't)
Personally, I just see it as a good use of space and something to make residents happy (as a kid I loved picking fruits).
I think the trees are these: https://en.wikipedia.org/wiki/Arbutus_unedo
Because all the fuss about insecticides and other chemical detergents in the bio industry in the last couple of decades, the food industry has done a lot to ensure that most of the chemicals are gone once the fruits are in the supermarket. Sure, it could still be better. But it is a lot better than a fruit tree that has been sucking up air pollution during its entire life.
Here is some more background: http://www.thewire.com/national/2011/06/ways-urban-gardening...