Yep. A "Q" multi-carrier fare will be booked in "Q" on all oneworld carriers, and so on. There was one major realignment when the alliance was kicked off, and I assume that it only included a limited number of buckets, beyond which each airline made its own letter; my hyphothesis is that with this realignment they expanded the number of standardized buckets.

Also, on transatlantics I am now seeing "S" as a published fare bucket, which appears to replace some of the "N" and fall a bit below it, so it's N S L at the bottom end (no Q & L switch here, and there was no Q).