There was a main street “beautification” in the 70’s in a NC downtown set up like this (only difference: square boxes). I later heard the explanation that the merchants didn’t want trees in the ground as they might “hide” the stores. ??? (which the huge boxes actually did to an extent and cost more than putting the trees in sidewalk grates).
Anyway maybe on this one, somebody couldn’t read the plans and the trees were supposed to go IN BETWEEN the vertical pipes? Not an infiltration bio-swale solution, that’s for sure.