I have 3 rwd volvo, and I live in Montreal, Quebec, Canada. We have real winters here, includeding the famous Icestorm in the late 90s. 4 Snow tire is a must, especially the two back wheels. I find that with 4 good snow (especially the back,the front is not as critical) I have confidence to go almost anywhere even during snow storms especially my 91 745t wagon.in the cities and hiways.

The only problem ocassionally I have is going up steep hill on very icy surface at dead slow speed,or Like you have to come to a stop and turn left and go up an icey slop. I guess having studded rear tires will resolve the problem,but I don't like the noise that comes with it.Also local laws is studded tires are only allowed during winter in quebec and I cannot go to ontario at all.

All I can say is the 745t wagon handles well with 4 snow tires even in heavy snow. Only problem is going up slowly on icy slops especially with sharp turns.
I am speaking from experiance of driving in these conditions for over 20 years. Have the rear wheel studded if you want extra confidence. Remember you can only have the snow tires studded when they are brand new. The front is not necessary. And when the snow tires are more than half worn out, use them for summers and then buy new snow tires for the next comming winter.

Good Luck.......