I was just talking to some friends, speculating about how the heck the crown truss will be built and we came to the same conclusion.
We think they are going to attach the big, long white tube pieces to the brown temporary triangles while the triangles are lying flat, then pull them up into the correct placement in the crown truss.
It looks to me as though the triangles can rotate, once the bars holding them in place to the columns are undone.
If they can get them all in the right position, joining them together and connecting the permanent (white) steel supports should not be an overwhelming challenge. The last step would be to remove the temporary supports once the crown truss is fully built.
At least that is what my friends and I, not engineers, are thinking.