As far as the trees being diseased, all city trees are unhealthy in one way or another. That is because their leaves absorb all kinds of exhaust byproducts, most of their roots are below concrete where they cannot get water or nutrients, and a hundred other reasons. Cities are just not healthy places for trees.
But that does not mean that we should not have trees in cities. Trees make us feel better, clear up the air for us and make us happier in general. What if a tree is not healthy -- it is not actually suffering and cannot pass the disease to humans. As long as it looks good and it is green, it is serving its purpose. I guarantee you that the new maples they put in will become diseased pretty soon.
So, good idea to call attention to this Paul, but someone should have thought of it earlier.