Thanks for the reply.
You said "Also, I interpret "tank" to mean tender."
That is what I thought at first too. The dispatcher's quote reads
"at Big Horn tank of 488 went from siding and engine 488 went from main line, extra 499 and 484 behind derailment. Tank is a long ways from rail will try and re-rail."
If 488's tank was the tender, and the locomotive split the switch with the engine going on the main and the tender going onto the siding, with the tender ending off a long ways from the rail, would think that the there might have been larger problems like burst water lines between the tender and the engine or even a separation of the engine and tender. I guess a long way from the rail might not really be as far off as I was imagining.