Has the Alignment Based Reference View been published, and if so, where?
The Alignment Based View (note that it is not a Reference View) is published within the core 4.3 documentation. For example, the list of concept templates includes a tag for each concept that is in scope of the AbV. These tags are also visible in the documentation of individual entities such as IfcAlignmentHorizontalSegment.
Lastly, the Entity List in Annex B is also useful to quickly determine if a specific entity is included in one of the 4.3 MVDs.
From the official list of MVDs, the AbV is awaiting final approval.
MVD Database - buildingSMART Technical
Just yesterday, I saw a change in the AbV documentation from github.
buildingSMART/IFC4.3.x-development: Repository to collect updates to the IFC4.3 Specification