I'd also like to point out that Noah in the post-floor 30 Eureka Orthos cutscene mentions that it was not the only such Allagan facility, which while out-of-universe is an open excuse to have another Deep Dungeon, it does open the possibility of one such facility being somewhere in Tural. Especially since the previously cited part of EE2 mentions they did conquer "portions" of it.

I've said it before (and I'll keep saying it), that I long for the day we're done with Allag, but the team has been very poignant about keeping that door open should they wish to use them again.