When a design file has multiple models, is it possible to create Map model reference to data from all other models?

Yes, it is possible. In the case of multiple models, create one model, attach the other models as references, and then create a map model from that model.

This should cascade all other reference files (models) that are attached to the composite model.

After creating a map model, you can simply use "Attach by Reference" in the Map Manager with "Attachment Method: Interactive" to attach your active design file to itself, selecting any model from the active file for attachment.