Those shots never fail to make me feel cold!
John, as I recall (and that becomes a dicier proposition with each passing year) Gordon used multiple stands (3? - 4?) all wired together to fire simultaneously. Yep, very large bulbs, but couldn't tell you much more than that. It was a frigid night, and he had some difficulties getting the wires run under the rails by the depot due to the cold, frozen ground. It took me hours to warm up back in the hotel after that session. The sad part is, I lost the digital files I shot that year in a multiple disk failure (two disc crashes just hours apart). They were also archived on CD, but where those CDs went is a mystery I've yet to solve. Shot film that weekend as well, which I still have, but my night shots were all on the DSLR.
If memory serves (but see above) you were there that weekend as well - 2005, I think. But I digress... obviously the technique you used for these is even more old-school, but it certainly did the job.
Scott