IMF IAB.mxf files are designed to be used in IMF authoring applications to create integrated mezzanine deliverables that include Video (including Dolby Vision) and Dolby Atmos audio.

IMF mastering tools that accept IMF IAB.mxf files are in the market and more are in the pipeline.  

For the near-term stay up to data on your customer's delivery specification to determine which delivery format is required.