First, MIP can only run models implemented in MIP. All models in MIP are executing PROC HPRISK code.
It depends on what you mean by "pre-built" Python model.
If you mean previously implemented model, then the answer is no. I know some customers are executing existing models (Base SAS, Python, etc.) directly from RFW.
If you mean atomic models estimated in Python, then the answer is yes! In fact, there is virtually no difference in the work you have to do to implement a model in MIP that was estimated in Python, SAS, or any other statistical language. All models (regardless of where they were estimated) require the same metadata setup to be implemented in MIP.
Hope this clears up any confusion. Let us know if you have any other questions.
-Chris Widman