The office building at the corner of Cambridge St and Everett St seems to be about the same height as what Harvard tentatively proposed along the eastern border of Smith Field. At 9:45 this morning the shadow reached almost to the edge of the parking lot, which according to the ruler in Google Earth, would be approximately 55 feet. Later in the day and as summer approaches, the shadows would be shorter as the sun moves higher in the sky.
The yellow line in this image from Google Earth measures 55 feet. The taller buildings suggested in Harvard's diagram are farther from Smith Field, so while their shadows would be longer, some of those shadows would be cast onto the other buildings.