What I can say though is that Zachery Group is an absolutely top end engineering and construction company and is headquartered in Texas. I'd be ticked off if they were left off the bidders short list.
Two mega companies that I have a lot of respect for wrt handling large projects on spec, on time and on budget are Zachery and Bechtel. High end quality controls and project management. In addition, they can flat slam resources into a project when required to meet tight timelines. I've worked with both of these companies.
One factor in the selection that was mentioned, is that the winning vendor has worked on border projects before.
If their past performance was good, and they were in on the Trump Administration Program, they would have little learning curve/lead time required. Not only lower risk, but they might have their costs dialed in to shave better prices. It was a competitive award.
It seems to me that this Program is on a very fast track (especially for Government) - they probably weighted past performance and readiness to meet schedule very highly.. They brief clip I heard of the winning vendor talking to the Government reps, was all about how the vendor was going to get moving quickly - panels up by the end of the year, in two weeks, including Christmas.