I was on a 2 (temporarily 3) lane road in the cenre (right) lane in freezing rain today and I was in traffic, boxed in. I had a car to my left, a car behind me, and a bus to my right.

I didn't realize the bus' lane was ending (and even if I did, I would not have yielded, as I was already halfway by him, and I had cars to my left)

So, 200-300+M from the end of his lane, this bus driver decides to slowly merge right into me and almost take my mirror off. I was passing him, and he obviously saw me. Once I layed on my horn, he backed off.

I know by law, I need to yield to a bus (although, this was a road, not a bus stop??) but I simply can't yield if I have cars to my left. I'm no just gonna hit the brakes...

Would I have been at fault if he hit me?

Even if it was a bus stop with a bus bay, buses are required to wait if your car is too close to the bus for you to yield right of way:

"142.1 (3) No driver of a bus shall re-enter the lane of traffic adjacent to a bus bay and move into the path of a vehicle or street car if the vehicle or street car is so close that it is impractical for the driver to yield the right of way."

The bus driver could be charged with change lane - not in safety.

If a collision occurred, based on section 10(4) of Reg. 668: Fault Determination Rules, where you are automobile A and the bus is automobile B:

"10. (4) If the incident occurs when automobile "B" is changing lanes, the driver of automobile "A" is not at fault and the driver of automobile "B" is 100 per cent at fault for the incident."