When he gets PR and assuming he's still in the USA, he should be able to fly from California to Canada. Not sure what would happen at the California airport though, I mean would it matter he's illegal in the USA and somehow they will detain him?.
If he crosses the border into Tijuana, not sure what would happen at the border on the USA side as he's illegal. Do the americans check the status of people leaving the USA?. Time ago I read in the news that they do.
From Tijuana he would definitely be able to take a flight to Canada if there is one direct, otherwise might have to fly to Mexico City or some other mexican city where there is a direct flight to Canada.
Perhaps some other senior member with experience could avise better.
Best of luck either way.