A transit visa is required for travel through Canada to another country by those persons who need a temporary resident visa and whose flight will stop in Canada for less than 48 hours. To obtain a transit visa you must provide specific evidence of your travel arrangements from your transportation company or travel agent.

To apply for a transit visa, you may be asked to show your travel tickets as part of the evidence of your travel arrangements.

That 30 minutes is very close. If the first plane should be late, you might miss the second flight. You should really allow at least a 2 hour stopover.
References :
http://www.cic.gc.ca/english/information/applications/guides/5256E2.asp