Sorry for the late reply. I missed your post as I was traveling for work this week.
To make it simple, Montblanc has a few types of movement categories:
1. Completely outsourced movements from Sellita or ETA or others. These are mainly found in the lower end Star and Timewalker collections and priced to be more accessible
2. In House developed movements from the Villeret manufacture or Le Locle manufacture. From Le Locle we have mainly the Nicolas Rieussec movements (all variants) as well as the Twinfly movement used in the Timewalker Twinfly. Note that all movements developments will only be done in the Villeret manufacture from this year.
3. Outsourced base movement with in house complication modules developed by Montblanc. Eg the Heritage Spirit Orbis Terrarum which has a Sellita base movement but a in house developed world time module
I don't think there is a movement number reference that clearly differentiates in house or non in house but I will review and check again on this
Hope this helps my friend 
Cheers
Robin