Just because you can't control it directly doesn't mean it's not a weapon. If the train on the Tyro Station multiplayer map is nothing more to you than a nifty visual gimmick or an occasional unexpected suicide, you must not be paying attention.
Next time, sit back and watch it work its murderous magic. You shouldn't have to wait too long to see a player or two get flattened on the tracks, but the real show is on the platform. Eventually, someone will stand too close to the edge, and that someone will be immediately - and viscerally - lacerated into peeled layers worthy of a dissection table. Yuck.
Strategy: Don't be an idiot
You can hear the train coming. Don't take chances, thinking you can squeeze off a few more shots before it arrives. In this particular case, reckless heroes go squish and scampering cowards live to fight another fight... plus get to kick around the heroes' bodies afterwards.