I myself have believe what Navion had to say about the tires. I only say this as he saw the tires himself and didn't hear it from a friends who heard something. However, I have to agree that we don't know where the cars came from, the condition of the storage or any information before the cars showed up at the dealership.
It is quite plausible that Michelin had a bad batch of tires as this is a pretty new tire technology with dual compounds being softer on the outside than in the inside (towards the center of the car). To me this sounds like with cold temperatures, the tire is going to have an uneven stress throughout the tread as the belts and rubber shrink at different rates. This is only compounded due to the different amount of rubber along the tread surface where it is thinner in the middle and thicker at the sides with the tread creating a perfect opportunity for stress concentrations. If the chemistry was a bit off on one batch and the tires hit cold temperatures, I could see the stress causing the rubber to split.
It sort of sucks if this is possible on normal tires because only a lucky few can afford heated storage or a second set of wheels for the storage period if the car has to be in the cold, however, as stated, we don't know enough and this may be an isolated grouping of tires.
The biggest thing I think is don't stress about this until your tires split, and if they do, they'll get replaced. At least the cracks happen on the outside and not inside the carcass. That would be scary!
