The M8189 can work in both Q/Q and Q/CD. There are jumpers that handle the grants. I used it in a BA11-M with a H9270 backplane.Another potential issue is that not all quad width QBUS backplanes are "suitable". The M8189 (11/23+) does not appear to be QBUS/QBUS, but QBUS/CD, and should probably be in the first slot on a compatible backplane.
http://www.bitsavers.org/www.computer.museum.uq.edu.au/pdf/EK-1T23B-OP-001 PDP11-23-PLUS System Manual.pdf
Page 64: "The KDF 11-8 microprocessor (M8189) is a quad-height module that must occupy the first slot in the H9276 backplane."
The H9276 backplane looks to be QBUS/CD only: https://gunkies.org/wiki/CD_interconnect
Even: were there actually any QBUS/QBUS quad width PDP-11/VAX CPUs?