Thank you for the question. I remember it now.
At UBC we do have the NITEP program, which is the native teacher education program. I'm sure it's mainly in English, but to answer your question, yes it would actually make a huge difference.
I could see where it should be almost hybrid though—their own language, as well as English—to be able to operate where they have to in English, yet be able to teach in their own language where they're teaching it. In other words, it's to gain the skills overall, but to use both languages. I have seen back in the U.S., where I have mainly lived, that some have both—for instance, Dakota and English—to be able to more appropriately teach either class and to be able to bring people together.
Absolutely, it would be very helpful to understand concepts and so forth in your first language, but it's probably prudent to also have English or French.