Grad students must have an average of 80% and at least 72% in each course for it to count for their breadth requirements (see http://www/grads/affairs/Handbook.pdf)
You can use https://ssc.adm.ubc.ca/fsc/servlets/SRVFSCFramework to give you a classlist for the classes you're teaching, or you can use the command "classlist [classnumber]" to give you a quasi-up-to-date listing.
The AMS has a database of old exams from classes at http://www.ams.ubc.ca/exams/index.cfm?subject=CPSC. Currently they only have exams from 315 and 430, but you may want to check there if you're planning on reusing things.