I can't say for certain what the reason is, but based on what I've seen in the game, I have a theory about this subtle suggestion that ties into a couple other things.
First, think about the images of the six summons learned throughout Luxendarc. Don't most of them seem a lot more artificial than what you'd expect of legendary beings in a Final Fantasy-esque universe? Examples: Hresvelgr is a huge black avian that first appears to be a jet plane, Promethean takes on the form of a speeding, flaming train engine, and Susano-o wields a radio/cellular tower like a sword.
Second, as you mentioned, is the presence of railways and electrical towers in Dark Aurora. In a universe as steeped in general fantasy tropes as Luxendarc, why would such post-modern detritus be found in this dungeon?
What ties it all together for me is an interesting little gimmick in the final battle, which I've described below. The details of said gimmick are a major spoiler for the true final battle, though, so don't mouse over that gray box unless you've already seen it. If you haven't yet, I highly suggest experiencing it on your own before reading the spoiler; it's a very entertaining reveal that should really be discovered first-hand to feel the full impact of its implications. Suffice it to say, though, that it should shed some light on the mystery, if you think about it.
In the final phase of the Ouroboros battles, the background changes, and Ouroboros claims that he's finally broken through to the Celestial Realm. Look closely at the rift in the background, and you may notice that it's an image being recorded from the 3DS' camera. This suggests that the Celestial Realm is actually our dimension and that Ouroboros' entire plot was essentially to break the Fourth Wall, step through the hole, and raise a nihilistic ruckus. Basically, this implies that Ouroboros' shenanigans, which had been gradually wearing the boundary between our universes thin for eons, caused random objects from our universe to appear in the Dark Aurora, which seems to serve as the proverbial no-mans-land between us and Luxendarc. The summons could be explained in a similar way: as mythical beings from our everyday cultural lore leaked through to Luxendarc, represented as objects from the Dark Aurora to give them definitive form, and given life and power through its all-pervasive magic, possibly as a result of the crystals' influence.
