I had most of the SB kits delivered by FedEx. For the really big stuff (as msot of the QB stuff would be, I'm sure), I did two different things:
1) I had the freight company (ABF I think?) deliver to the local bonded warehouse in Ottawa that they deal with. When it arrived I went to the warehouse and picked up the paperwork from them and took it to the customs office myself, paid my duties and got the release paperwork. Took the releasepaperwork back to the warehouse with the rental truck. They loaded it on the truck for me and away I went.
2) For one of my big subkits I drove down to the Watertown ABF frieght depot and drove it back across the border myself (stopping in to pay duties).
Basically, you can either clear customs yourself (as I did for both options above), or you have a customs broker do it for you (as is done when you use FedEx or UPS - in some cases for big items they will ask you if you have a broker, or if you want to use them as the broker. Usually it's hidden from you, but you'll see a brokerage fee somewhere in their charges). Vans uses ABF for the big stuff (at least, they did when I was building). If you have ABF ship right up to canada, you'll have to talk to them to arrange a customs broker, or else do it yourself as I did in case (1) above.
If I were to do it again, I would not do (2). Not much savings after you factor in the gas, and lot more time and hassle. The first approach worked very well for me.