I've got two cyclocross bikes, one with campagnolo mirage ergos and shimano cantilevers, and another with sora levers and weinmann cantilevers and both work fine (after a bit of effort to get the cantis set up right). There's usually no problem using any road levers with cantilevers - it's only v-brakes that don't work.
I did find setting the levers higher up the bars than normal helpful. It looks a bit ugly but I find you get more leverage that way.
Hope that's useful,
Johnny