CS Major at UBC - Just how difficult is it to attain?

It seems that to major in CS at UBC Vancouver, students must compete based on their freshman year academic record. Does anyone know what % of those who aspire to CS major actually are permitted to progress with this degree after their first year? I have found no meaningful data from the school’s website and UBC’s peer advisor provided only vague encouragement. I am seeking reliable info on this. And what are the options for those who are not permitted to progress with a CS major? Do they by default enter into another major or must they compete for a major? Many thanks.