MJLC uses only fully in-house movements in all their watches.
They also sell movements to several other brands (Audemars Piguet, Vacheron Constantin, Cartier, Van Cleef et Arpels, Panerai among the main brands).
They used to sell movements to many more brands (Patek Philippe, IWC and Breguet for instance).
They used some outside movements too in the past, the most recent models being very probably the "Le Club" series in the early 70s, so it was stopped around some thirty years ago. "Le Club" was a more economical range of models, having a mainstram outsourced movement.
Like "Le Club" the blog is still "outsourced" for its "engine" today.