In Arrow season 1 episode 18 Salvation, we learn that Starling City doesn't currently have a subway, it used to, but it's now abandoned. The tracks of the old subway were used by a villain in that episode and the subway logo was shown:
In season 3 episode 7 Draw Back Your Bow, Arrow has a fight at what looks to be an abandoned station of the same subway (with the same logo). When he and a villainess fall down on the tracks, a train appears almost immediately. But this time, there is no indication that she planned this and somehow made the train appear at the right time. To me, this seems to indicate that the subway is regularly used.
What could explain this? Did something change in the time between the two episodes and did (parts of) the subway network start to be used again? Or is there some other explanation why would a train ride on an abandoned track?