I was in the tire industry with various companies for about 8 years, so I want to say a few things about the tire discussion.
That "M&S" rating on tires is garbage, they stamp it on everything, don't trust it. It is based off of some formula that uses the ratio of void space to tread blocks on the tire. Some high performance tires are rated M&S and you REALLY wouldn't want to drive in either the rain or snow with them!
What you want to look for is the mountain/snowflake symbol on the sidewalls.
If it doesn't have that stamp on the sidewall, it is not rated for winter conditions. And this is a legit rating, unlike M&S.
There are an increasing number of tires that have come out with this rating in all season models in recent years, the BFG A/T is one of the oldest, but as it is, the design has gotten old and they are no longer what I would consider the best option right now.
I've got the Goodyear Duratracs on my Cherokee and love them in the warm and cold months. In the winter they grip just like other true winter tires that I've had on other vehicles of mine. I live in the Edmonton region, and it gets COLD around here in the winter. And the cold is what kills the traction on normal tires, they can't warm up and stick to the road. Also winter-rated tires have a lot more siping (thin cuts/divisions) between the tread blocks to improve grip over larger tread blocks. That's why mud tires really suck in icy conditions. It's like trying to get a grip on something with your fist closed, and you're pawing at the surface with your knuckles, it just doesn't work.
I know there are a few other tire options out there, just can't think of them off the top of my head.
I've been pretty happy with my GY's so far, and have had at least one other friend run them on his F-350 for about 100,000 km's and he was very happy with them as well. They do hum a bit on the road as they are a bit aggressive, but you're not likely to get stuck in snow or mud unless it's really deep, in which case you just have to pull out the winch.
As for trailer tires, I've never heard of winter-rated trailer tires, I doubt they exist.
Chains - you always want to put them on all 4 tires of the vehicle so you have grip on all 4 corners. If you just put them on 2 tires, then the other tires won't have grip and you will fish tail or spin. It would be like putting 2 brand new tires on one axle, and two bald tires on the other axle and then driving in rainy conditions, you're going to slide eventually.
Bearing that in mind it makes complete sense that they require chains on the trailer as well, given the hazardous conditions. Without chains on the trailer, it would slide off the road and then pull your truck off too.
And the situation regarding snow tires in Quebec is really interesting (to me anyways) - the gov't compiled a list of all passenger car tires that were rated for winter conditions and handed that to the police that were then told to hand out tickets to anyone that was driving with tires that were not on "the list". Well, you may be able to see where this is going...
The gov't bureaucrats that did the compiling of that list were not 100% accurate, so some members of the public were handed large fines because their tires were not on "the list" despite the fact that they were indeed rated for winter conditions. One of the guys that worked for the same company as me at the time got 3 tickets for this. He was going to fight it, but at the time it didn't look good for him.
I've been out of the tire business for a little over a year so my info is a touch out-dated, but the last I heard was that only passenger cars (and most small/medium SUV's) were required to have winter tires. Pickup trucks were not required because at the time the legislation was passed, winter tires were not being produced for all sizes of truck. The tire manufacturers have begun to catch up in this regard, so I imagine that the legislation may be updated as well.
My strong guess would be that similar legislation will be passed in the rest of the provinces at some point. We live in a northern climate, it just makes sense that we should have the appropriate safety equipment installed on our vehicles to be able to handle the winter conditions.