I do not see why the Prime Minister should have resigned at that moment. He could have, but the House was to meet on the following Monday. I assume the results would have been that the House would meet, there would have been a vote taken, and as a result of that vote the government would have been defeated. At that point, Mr. Dion would have been called upon to form the government.
If he had resigned at that point, I would imagine she would have simply at that point called upon Mr. Dion and would not have had to wait.
I do not think he would have had to resign at that time. I think it would have been appropriate for him to continue in office until the following Monday.