Looks like they were only a few weeks behind. The official groundbreaking ceremony was yesterday. Although, from what I saw, it looked like the built a small sandbox, filled it with earth, and dug into that, leaving the actual ground on the site unbroken.
On the wall of the site along Post Oak a new banner has popped up - sorry I couldn't get a clear shot without the sign and light pole. It was all I could do to get one without cars in the way:
Here are the three pictures close up:
And a REALLY short Chron blog post about the site: