From what I've seen around me, firefighters tend to be pretty careful drivers even when running with flashy lights, but there was an unfortunate break down here. Condolences to those involved.
But, large boats can turn if the channel allows and trains can't, and boating tradition is clear that vessels restrictred in their maneuverability have priority, so trains win. ;p
Now arguably this was not a right-of-way situation; but I guess you could argue that stationary objects have right-of-way over vehicles.
There are roughly four airports with railways crossing the runway, although three of them seem out of use.
(I'd guess the train takes priority in normal use, as the schedule is probably less flexible, but given notice of an emergency the train could be asked to stop.)
-A320 Captain