The City Forestry Division and the Shade Tree Commission have provided a database of trees in the city, where one may find a lot of information about specific trees. One can use the mapping tools to find individual trees, along with information about the tree's health, if any work has been scheduled, etc.
http://www.city.pittsburgh.pa.us/cp/html/treekeeper.html
Forestry Division page: http://www.city.pittsburgh.pa.us/pw/html/forestry.html
Shade Tree Commission page: http://www.city.pittsburgh.pa.us/cp/html/shade_tree_commission.html