Photo Mechanic views the embedded previews in your RAW files. It seems that Capture One is not touching whatever JPEG Photo Mechanic is finding, so Photo Mechanic will continue to show the original JPEG embedded in the RAW file. If Capture One won't update the embedded file, I would recommend having it save out a JPEG that is representative of the processing done by Capture One. Photo Mechanic will join that with the IIQ file on the Contact Sheet and show you that image instead.