Thanks for the detailed explanation Kevin. Much appreciated!
Your night shots completely avoided an effect I usually see (in mine and others' images) in flood-lit night shoots - indistinct, blurred out steam and smoke. The only times I've avoided that effect have been shooting on the Nevada Northern with Steve Crise's strobes - and years ago with Gordon Osmundson's old-school flashes. That's why I wondered if these were strobed.
I went back and looked at your shooting data and realized you were using some impressively short (for night stuff) shutter speeds. I see now that you've really cranked the ISO (ain't newer sensors great!) but those new lights of Pete's still must be quite impressive to allow 1/20th and 1/25th second exposures, even at ISO 4000.
Bottom line, I love 'em - well done!
Scott