I'm not a concrete industry professional, but I found the stemwall forms (the flat panels with "Advance" all over them) shown in Brendan's photos very interesting.

Mostly I'm familiar with wall forms braced with 2x4 etc lumber, like this:

If you look (in particular) at the last photo Brendan posted (the inspection pit), you can see that the forms are braced with steel sections. I didn't quite understand how that all worked, so went looking for more info on Advance Forms. Their website is here:
http://www.advanceconcreteform.com/formsIt appears that our
roundhouse engine house is using standard 2' panels, with occasional smaller versions when necessary. There are standard steel corners, two of which can be seen in the inspection pit photo. Here is a closeup from the Advance Forms site:

As you can see in that image, there are 'latches' that hook the vertical steel corners to the 2ft panels. And the panels similarly hook to each other where the stemwalls are straight. One can browse the Advance Forms website to see there are a variety of other components available for situations that may/may not be present in our 'pour'.
FYI, the panels themselves appear to be "HDO panels", a plywood core with a 'High Density Overlay' (fibers mixed with resin) which makes a smoother finish than plywood and results in a highly durable surface, compared to standard plywood.
These kinds of forms systems are likely more expensive material-wise than the all-wood versions, but pay for themselves when considering the labor involved to set them up and take them down. In the long term, for a forms professional, they cost less than traditional (mostly) wood forms.
Great photos!