It would have meant that he was freeing a military plane in accordance of Defence department guidelines on rescuing Canadians.
http://cjob.com/news/index.aspx?dir=nation..../n0720103A.xml
They had already been rescued from Lebanon, as it was rather impossible for him to take the plane into Lebanon proper where they needed rescuing. What he was doing was using his plane to transport the rescued people back to Canada.
Also, I'm curious if you just linked to that article hoping I wouldn't read it? Nowhere does the article say that all assets of the Defense Department (military planes, which I don't believe his is classified as) need to be used to rescue people. It says that it is that the Government has a responsibility to rescue its nationals, which is what it is doing. They had the planes for all the people from the ship, and his wasn't taking all of them. The planes were not crampped up. Those were the boats. I guess the PM could have taken a commercial flight back to Canada, but that would have meant we had that much extra to pay, and nothing extra out of it.