Following the comments on this thread (as always, an education!), I wonder about the actual original requirement. The question was posed about OWB vs MSP, but I wonder if that hits it quite correctly. OWB and MSP are both management tools, and as alluded to here, both operate on different principles and with different algorithms.
If there's a genuine need to pass the project plan - in MSP format - to a non-OWB user, it stands to reason it would be passed so the non-OWB user can make updates. If this is the case, unless there's a way to get those updates back into CA PPM, they will get lost in transit. And, how would you identify which updates were made because of the different algorithms and which were intentional?
If, on the other hand, the purpose of passing information to the non-OWB user is to report status or progress, then I submit there are better mechanisms, not subject to the vagaries of a planning tool. A representation of the gantt chart in a custom Jaspersoft report would be one such mechanism. Alternatively, dropping the plan into Excel and formatting it there might work just as well.