Let's say the tangos are in the green carriages (middle of
train), how fast can SOF/STAR reach them, even if they force a
sudden, total blackout?
Let's say the tangos threaten SMRT "if you dare blackout the train
or the tunnel, then we end all lives Heero Yuy style!" So the
tunnel and train will be lit. Even if the lookouts at both ends of
the train kenna sniped (wahahah, the scenario must take place in a
very curved portion of the tunnel, so bullets cannot reach the
train from far), the good guys still cannot reach the train fast
enough. The element of surprise and shock will be lost.
PS: Any CS map for this scenario? 
