I've been checking with my BMW factory pals in Steyr Austria where they build the engines. My wife's cousin works in the assembly hall.
Yes there is a known problem with the pcv - mainly on larger engines that are used for very short journeys in extreme cold climates.
Apparently the condensation that can form in the pcv combines with the oil to form an emulsion (the yellow coloured gunk that can also show up on the oil filler cap) which can actually freeze and block the pcv causing the pressure that we know about as well as seriously damaging the turbo.
BMW are rumoured to be developing a heated breather for extreme cold conditions.
Nothing to worry about for those who are aware of the problem.
If you make repeated short journeys in sub-zero temperatures you just need to check for the 'mayonnaise' forming and change your oil accordingly.
Nothing would make me go back to fitting the old 'loo-roll' filter.