Sharing data between software packages is very common in production. It may be texture data, simulation data, or any number of assets created with a commercial or proprietary tool.
One such example is attaching data in a simulation, perhaps in Houdini using Attribute Create, and then rendering it with assets in another software like Katana with the exported data.
Important things to remember when exporting the asset are there are two main types of data, one is varying called a Primvar, and another is constant called an attribute in the RenderMan vocabulary.
Two common exports that are supported, but not exclusively, are Alembic caches and OpenVDB files. This data would contain the exported attributes. Each content creation package has their own workflow for attaching and exporting this data, please consult their documentation on creation and export.
Once in another software package, for RenderMan to read the data, you should create a PxrPrimvar node. Supply the node with the data name you used in the original creation and the same type, be it float, color, etc. Keep in mind that evaluation of this data may be expensive depending on its type/content and size.