I hope that too (co-developing).It's kinda ambiguous whether china simply invested in it or was part of the development process . Personally I hope it's the latter because that way it could use some of the S-400 technologies on upgrading HQ-9's or something.
Also, is it just me or does the S-400 TEL look less mobile than the S-300 series (and HQ-9?) It's now a trailer with the TEL behind it rather than a whole truck thing dedicated to launching missiles.. Would this effect the S-400's mobility?
You have too look hard to see if they are same launch tubes as S 400. Hope someone is able to definatively prove they are the same?