More than likely the planter boxes (raised beds) are watered by drip irrigation or hose watering. You can see a hose in the walk space between the planters.
What is little understood in the gardening world is that sub-irrigation is a much better way to irrigate these boxes. There are many books and blogs about top watered raised beds but little about sub-irrigated beds or wicking beds.
It appears that the boxes are lined. In any case they should be lined with sheet plastic and a raised bottom created to hold water. A wicking system would then move the water up by capillary action.
This method provides the ultimate in even moisture on a consistent basis. Plants thrive on this with the result that vegetable productivity may be as much as doubled, at the same time using much less water.
One of the goals of the Center for Urban Greenscaping will be to test various systems of sub-irrigation with the goal of finding the most productive and easiest to build.