Nice positioning for the trees, with potential for them to become significantly expanded overhanging canopies, to a certain pont -- planted in the middle of the north sidewalk. The grate on the ground, while bigger than many other Toronto grates, is extremely small by many heritage city standards (e.g. some huge grates I've seen, about four or five times as big). The tree will continue to require human assistance to survive once it becomes big enough for its trunk to choke the grate and prevent further water from filtering down.
Even a mere 6" wide trunk can choke water away from a 12" wide grate because of the way the trunk expands outwards at ground and below. Waterproofing the tree itself from being able to be watered by rain!! Many street designers get caught off guard by that!!!! Because of this, grate size should be least 3-4x wider than the diameter of the grate hole, as a result. But this pictured grate, while an improvement by Toronto standards, is less than 2x the width of the trunk hole. In historical times, that is why you see well-designed huge old-fashioned grates for city trees (the circular wheel-shaped ones) look so much better designed. Big enough that the tree is self-watering by weather, with no human watering in times of lean city budgets, so the tree can kind of limp along until better city budgets a decade later, etc. Those 19th century city trees and early 20th century trees are still alive today.
It really seems, that in some parts of the world, some 19th century and early 20th century city-tree aborists have done a better job than some of the 21st century, allowing massive
100-year old beautiful tree to survive in the middle of a downtown heritage district containing a grand train station like our Union!!!! For many decades, Toronto has been an absolutely terrible place for downtown city trees, and while this is gradually improving, it is still fully an abysmal record even today.
That's sort of a non-answer.
It is a generic answer, but an answer nontheless.
A
real aborist inspected our own trees (we unusually have a century-old
redwood tree on our Hamilton property!) so I do definitely have something to say about these Union trees.
I believe (although I'm not positive), that there is usually a contract provision regarding death of trees within a certain timeframe, which protects the owners from exactly what you describe. Road salt is out of their hands.
I pretty much believe it doesn't always happen in all cities. I hope the provisions are stronger for Union. There's many North American cities that just dig a hole in the middle of the road and plant a tree, only to see them die. And other times trees abandoned after an expiration of a some kind of contract or city funding cutbacks -- fertilization, waterings and salt-washing stops -- and many downtown trees die without human help.
The front of Union is special and any trees planted there need to live for at least 10, even 20 years, or more, if that can be possible at all, so hopefully a super long term is included in the contract (doubtful), so we don't have a
mink mile situation. Also, in some Canadian cities I've even heard of them avoiding road salt on certain historical districts, utilizing other gentler methods or reduced salt (aggressively avoidance and remeditation of oversalting incidents), for one reason or another such as brickwork and/or vegetation, so in theory this is a special enough of an exception for co-ordination with road maintenance (there is precedent elsewhere) -- if a few blocks could become salt-free zones to protect heritage districts, leaving minimal salty slush rolled in from elsewhere rather than leftover excess salt rocks that takes a full month to dissolve away. Salt is known to damage brick over time, too. Considering we've put such an expensive multi-million-dollar brickwork pattern on the entire Front Street block. I'm currently just a little skeptical about the city's long term plan for keeping that location studiously in ship-shape 10-15 years from now, without salt-weakened snowplow-chipped bricks, a bunch of asphalt patches, and a couple of tree stumps between struggling semi-grown trees... But I'm hoping!
So I admonish -- I am skeptical all trees are going to to simultaneously be able to grow to even to 20 years without at least one stump in between. It can reliably be done, but this specific grate design doesn't allow self watering to succeed once the trunk reaches approximately six inches wide, if the city decides to chop maintenance budgets.