I travelled to Moscow, Russia, recently. Apples were commonly used as
street trees there, although due to fruit drop and other problems, I
don't recomend this. Basswood (Tilia species) are commonly planted in
Chicago. No one uses them, but the flowers could be used in tea.
Frankly this seems more hazardous, in re. urban air pollution, than
fruit because of the higher surface area (exposed to smog) to volume
ratio. I've never seen *intentional* edible landscaping of any sort
practiced in Chicago, though. Do New Englanders tap their street
maple trees? I forsee a "tragedy of the commons" problem arising
since (at least in the Rust Belt where I currently live) property
rights to streetside areas have eroded to the point where they are
practically city property.
Street hedges seem to pose less of a hazard from fruit drop. Many
plants seem suitable: nanking/bush cherries, Rosa rugosa, kumquats
(subtropics), highbush cranberry (esp. for shade), even severely
pruned mulberries. However shrubs don't shade drivers from the summer
sun. Again, the "Commons?"