Again, it's on a case-by-case basis. For example, if someone says, “I'd like to bring my vehicle in for three months,” and something happens and three months become four months, they can simply contact Transport Canada and say, “My permit number is such and such, I had stated three months, but I need a little bit longer.” As long as it's for a valid reason, the permit is extended.
Evidence of meeting #142 for Transport, Infrastructure and Communities in the 42nd Parliament, 1st Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was border.
A video is available from Parliament.