I don't know ... I am an engineer and know plenty of engineers... and we don't really use Macs... I have however seen some NASA engineers with Macbook Pros... but due to cost, most of us contractor-based engineers work with Linux and Windows
I see a lot of this, too. I'm removed from the field now, but even a few years ago it was becoming very common for engineers to carry around a Macbook and have a Linux workstation.