Raise the Hammer

"I know it's just an illustration, but what kind of trees would be getting planted? As you can see they already obscure the store names. Would they need to be cut down at some point for growing too large?"

There's no question that trees soften a landscape like this and make it more appealing. One element that often goes unconsidered, however, is the requirements of the root ball. The rule-of-thumb tends to be about 1 foot for every inch of trunk diameter, so if you're talking about a mature tree with a trunk of 4-6 inches, you're looking at a substantial root ball (to say nothing of the root system that will eventually arise from it).

This is why, for example, the median trees along Main West near MUMC are both relatively slender (2"-3") and centred in a large hardscape island. For a larger greened median (as you find on York or the Gore), large trees are possible because they can grow unimpeded by roads/roadwork.

On a stretch of road like Main that is prone to over-salting in the winter and perennial resurfacing in the summer, trees can be scorched at the best of times. If the root ball is too big for the space provided, the tree will suffer or it will find a way to thrive, and that often winds up compromising water/sewage lines. Penny wise, pound foolish.

Columnars are generally best for most compact city settings, because you get desired height without too much spread. Across the city you'll see regular plantings of of Ginkgo, Pear, Poplar, Maple, Hornbeam and so forth as columnars because they satisfy the need for predictable outcomes.

You can also incorporate large, broad-trunked trees into settings that are dominated by hardscaping, but you need to allow the tree to thrive. These kind of plantings need to incorporate realistic parameters for future growth and allow for expansion (the inevitable horizontal spread), and any such transplants need constant care in the first year or two so that stupid stuff like water stress doesn't flat-out kill the tree before it can even get settled.