los angeles city hall, julius shulman 1933 reference marked
I've chosen and marked two points of reference on this image. One is the southernmost corner of the Hall of Records where it appears just above the International Exchange and Savings Bank (marked with a red dot). Secondly, I've chosen the ninth verticle window (technically this is actually the tenth verticle window but I'm discounting the verticle window closest to the corner of the building) in the Hall of Justice where it appears directly above the cupola of the Baker Block (again a red dot).
Using those points of reference, I've now laid out an azimuth from each point on this 1927 image of the civic center...
los angeles civic center 1927 with reference
which gives us this intersection which seems to correspond to the Aliso side of the main train platform at Union Station. This is admittedly a somewhat imprecise method but I think it gives a good approximation of Mr. Shulman's likely position.
Staying with the red dot theme, here is, approximately speaking, Mr. Shulman's spot. I think.
los angeles union station, julius shulman
Actually, I think the little structure on top of the train platform wasn't there when Mr. Shulman exposed his film. I think the rebar we see in the image was going to be used to anchor this structure. So he was standing back from the front edge looking across the foot print of this little building.