"some minor fires will turn into major explosions if you put water on them."
Agreed, particularly fuel. However, it doesn't have to be an automatic system, or a system using water only.
A system manually operated from a central control using a chemical fire suppressant, or even a cocktail, would much reduce the risk to firefighters, and would retard the spread of fire and therefore the length of subsequent disruption.
you would need to hive a qualified fire fighter permanently stationed in the control room to make the decision about which suppressant to use. Before they could make that decision they'd need to know what had caused the fire. In this case it's thought to be a truck carrying Phenol. If the wrong liquid is put a chemical fire the result could be a major explosion.
Can you imagine the complexity of a system that could deliver a variety of suppressants along a couple of 50km tunnels.
On balance I think the right system is in place. Along the two tunnels are regular links to a central relief tunnel, the air in this tunnel pressurised to prevent smoke and fumes entering. this tunnel is wide enough for rescue vehicles to drive up & down.
I think that there is some confusion over which vehicle caught fire. Some sites are reporting that there was a vehicle carrying phenol near where the fire started. I would be surprised if any vehicles actually overturned before the fire. I do wonder what inspections are carried out on vehicles, especially lorries, before they board the train to make sure that they are in a good enoug condition to travel and are safe.
I have fought a fire involving high explosives and toxic chemicals from behind a manually switched heavy duty drencher.
Under all normal circumstances, no matter what happens behind the drencher the fire is contained. More importantly, when you face the fire you know you have only to take one step back to regain comparative safety.