the best way to be sure to get an upgrade is to look at www.aeroplan.de and then galileo on the sidebar.
to see if there are seats avaible in c for upgrading just look at the Z booking class
works great
two weeks ago a planned a trip to jnb this way and 5 minutes later de z class was corrected with two seats so itīs a good indication first look then book and then call
or you can book a trip online and hold it for 72 hours and then call and confirm your flight if there is availibilty