insulation of a basement
I'm in a similar climate, and what you describe is standard aside from the insulation. Rock wool is no longer used in favor of fiberglass or spray foam where I am. I have no reason to think that it's a problem, though. 

Convection isn't a concern outside the heat envelope. Condensation isn't either because it's on the cold side. 

That said, some recommend against vapor barriers in basements due to the dual-membrane situation they create in conjunction with the foundation waterproofing. This can trap moisture and promote mold and decay. It was probably installed as temporary covering for the insulation.