I don't know who pruned those trees -- but it is true that the pruning that's good for the health of street trees is pretty different from what could be done in a suburban yard or in the forest. Street trees not only need to be planted thoughtfully to make sure they won't grow into power lines, they also need to have low limbs removed so that people can walk on the sidewalk and trucks don't rip off their street-side limbs.
A limb pruned carefully is always better for the tree than a limb broken, so healthy street trees are "limbed up" to remove branches that are likely to be broken. And yes, that can make them look a little lollipop-y when it's first done, but they will fill in next spring.
And it is better to remove potential-problem branches early, while they're small, than to wait until they are large enough to actually be a problem but are also a proportionally more important to the tree.
If you're still reading, you might be interested in the Pennsylvania Horticultural Society's Tree Tender program, which teaches all this and much more about planting, pruning, and maintaining street trees in the city. The next program is coming up at the beginning of October -- go to
http://www.pennsylvaniahorticulturalsoc ... ining.html for information!
