They posted the site plan today. The elevations are on page 26.
ftp://ftp.ci.austin.tx.us/ATD_AULCC/...tial_PLANS.pdf
471 feet 9 inches to the top of the mechanical penthouse
450 feet 9 inches to the main roof.
431 feet 9 inches to the 35th floor (highest occupied floor).
107 feet 9 inches to the parking podium.
The elevations also show that they're planning removal fiber glass panels that contain planter boxes. So I guess they're planning to keep the greenery on the parking garage.