With MicroStation CONNECT Update 12, Picklists are added to the C++ MicroStationAPI. Hoorah!
The functionality offered by C++ is similar to the .NET API. However, C++ doesn't provide the CustomProperty::PickListName property to assign a Picklist to an Item Type Property. In other words, we can create a Picklist programmatically, but we can't use it. I assume that this is an oversight in the MicroStationAPI?