In order to get a work permit, the company has to apply and conditions have to exist that they are unable to fill the spot by qualified Canadian pilots. Meaning noone who has applied meets requirements or noone is interested in working for them. They then have to prove that they had put out job postings for a certain amount of time and that the position was not filled. The work permit is usually good for a year but I believe can be extended. Its a bit of a hassle on the part of the employer and you do need a job offer before you can apply.
Most companies wont put in the effort on your part especially if you're not high time.