Matt,
I agree with Been There, you definitely need to ask the folks you’ll be working with/for, as I did before I wintered at Pole a couple years ago. I’m not an ironworker but I am a construction engineer and I didn’t really think that the footwear selection available at CDC (the Clothing Distribution Center in Christchurch, where you will pick up your ECW (extremely cold weather) clothing) was appropriate for heavy outdoor construction. Another factor with me at least is that I wear size 15 🙂
Foot comfort is important. In any case, to avoid any uncertainty I packed my own comfortable (and very bulky and heavy!) pair of insulated boots, and I suggest you do the same. Especially if you are going to Pole as I suspect, lots of heavy iron going in there for the SPT (South Pole Telescope) ground shield foundation.
Unless things have changed they do not need to be steel toed.