Since there seems to be no support for encoding an MPEG IMX stream into a Quicktime container out of the box in Premiere CS5.5 I have managed to cheat IMX in there by using Quicktime component files from a Final Cut Pro installation. This seems to work fine, I now see all kinds of IMX options under the Video Codec section in Quicktime export, but there is one problem...
There is no way to edit any codec settings to turn off Quicktime Gamma correction, as you can do if you are exporting to Apple ProRes. What happens is - I need to add a Gamma Correction filter to every timeline to make it darker, because the default encoder settings automatically include some gamma correction that makes all rendered videos slightly brighter than they should be. This is a bit annoying.
Does anyone know if there is a way to disable Gamma Correction for MPEX IMX Quicktime files? Also, when will Adobe include native MPEG IMX encoder support? A lot of broadcasters in Europe (especially Eastern countries) still use IMX as their codec in their playout facilities - sometimes in Quicktime containers and sometimes in .mxf containers. Premiere needs to supports this.