I have that same lens and my aperture doesn't work at all on the BMCC lol
(but it works fine on a Canon DSLR) .
It's probably not a BMCC issue but rather the mechanics of the lens? The apertures in a lot of lenses are lubricated with fine oil, the oil may solidify or become less effective at low temperatures, causing the aperture not to respond.
Given that my lens like that doesn't respond at all I would hazard a guess that the BMCC emits barely enough power to drive the aperture servo and so the suggestion above would have an even higher likelyhood.
Have you tried with multiple lenses ?