I have the G85 but not the lens. Have mounted several oly lenses on panny bodies. Dont really see any problems. You can go to youtube and do a search. quite a few reviews of exactly the G85 & Olympus 40-150 /f2.8.. Seems fine
Please understand although Olympus and Panasonic use the same image format (M43) and lens mount that's where their similarity ends.How they implement
their camera controls is up to their respective rights.M43 is a loose standard.To appreciate this fact even their EVFs (electronic viewfinders are not compatible)
so only image sensor and lens mount electrical contacts are common.That said Olympus try to make their lenses work their best in Panasonic bodies so they have
tweaked the lens firmware in this respect and as for 40-150 F2.8 pro it's last update (lens fimrware) for Panasonic bodies is M.ZUIKO DIGITAL ED 40-150mm F2.8 PRO 1.2 Nov. 22 2016. I assume no major issues to date. Issue with G9 is another matter let's hope Olympus is looking into that as well as Panasonic.
Do note lens firmware update is only for Panasonic bodies.Please read their instructions on how to update carefully. Panasonic camera must be updated to their LATEST camera version first! Make sure battery is on full charge and lens attached to camera, be patient it will take minutes so don't panic and start unplugging things.Also Olympus say software use is " AS IS" basis.The normal legal disclaimer. Olympus udate is via PC online so no downloading to memory card.Oh you must first download it's firmware update app if you have old version.
OLYMPUS Lenses firm update for Panasonic camera body