DCA switches between the daytime version of GotG: Mission Breakout and the night time/Halloween version GotG: Monsters After Dark every evening with (more or less) the flip of a switch. So long as you have a ride/queue that is media/lighting/sound heavy (and rely less on practical effects) the switch could happen just as quickly. No reason you'd need to go crazy with Midway Mania's queue to convert it which means all you would really have to do is worry about the projections (which again could be switched more or less instantly). As it seems like Runaway Railway will also be VERY media heavy (even if it is being projected onto practical effects), one would imagine that a Halloween/Christmas overlay for that attraction could be switched on just as quickly.