NOOB (Not one-off Britishisms) asks UK residents how they pronounce “negotiate”: ending shee-ate or see-ate. I am an Ireland resident, but I’m answering for myself. And I’ve considered all words in -ciate, -tiate . I’ve arranged them in order.
Either -s- or -sh-
Now -sh- once -t-
The last section is book-words where I would have guessed -t- as a spelling pronunciation. Interesting that neither -s- nor -sh- appears to be my default for novel -tiate words.
The above rankings are by no means definitive (even for me, I mean; let alone anyone else) and I’ve shuffled them several times in the 20 minutes I’ve spent writing this.