I have a 335i with summer tires on.
You can get by if you know what you are doing...and I mean, really know what you are doing and have experience driving RWD cars in the snow with summer tires.
At a clear intersection, I applied a little more throttle than necessary (maybe 500 rpm more) and that's all it took for the tail to kick out and the car to do almost a 180.
This was with traction control FULLY ON, not off, not DCT!
Like I said, if you know what you are doing, you are fine with 3-4 inches of fresh snow. If it's 6 inches of fresh snow and there is a slight grade to the road and you are dead stopped, you wont be going anywhere.
I could not make it up my driveway in reverse when there was 2 inches of snow. I had to take a rolling start at about 5mph from the street and aim the car right into the garage. lol
This is how steep my driveway is. (I know the marble does not help with traction either but just giving you an idea of how bad the tires are in the snow) :
