From the Famitsu interview, provided by
@VSXIII:
• Tabata reveals that, even before Type-0 HD, members of Hexadrive had already been cooperating with Square Enix on a RPG for next generation consoles. This title turned out to be FINAL FANTASY XV.
• Timing-wise, Hexadrive have been involved since XV's development still operated on the Ebony engine (before integration with the Luminous Studio engine was completed). More specifically, the start of this collaboration would have been a little while before the E3 2013 reveal as XV (from the former name Versus XIII).
• Hexadrive's knowledge of HD development gave Tabata the confidence to entrust them with Type-0.
• Long story short, Tabata makes it sound as though Hexadrive largely taught SE how to develop HD games (this is an interview where the Hexadrive CEO is present, so I don't think it sounds more important than it actually is). The original KH-style game play for Final Fantasy Versus XIII turned out to be difficult to achieve, so the game's form has changed.
• Naora and Tabata reveal that SE and members of Hexadrive went to an actual cave in Chiba Prefecture (next to Tokyo), collected data, and used them as reference for creating the cave in Episode Duscae.
• Matsushita says that Type-0 HD was a very easy collaboration with Square Enix. SE worked largely on the 3D graphics (including character models in cutscenes, I presume), and Hexadrive worked mostly on 2D graphics (UI, icons, making the forests on the world map look fuller, etc.), and the lip sync.
Source:
http://www.mognetcentral.com/threads/final-fantasy-xv-general-news-thread.3288/page-35#post-21900
