I would believe that much of this is true. Canadian immigration and refugee policies are chaotic, unenforcable, and leave MASSIVE loopholes for immigrants to march through. People may land, declare refugee status, and then melt into Toronto, never to be tracked. They may try to apply for gov’t money, but they would not be well tracked then either. Certainly members of terrorist organizations may slip through - there is no doubt - many of these have been arrested.
Too, it is true that when a member of the (right-wing) opposition suggests that something be done to tighten our borders, they are painted as racist fear-mongers who are painting all immigrants with the same brush, so the issue becomes lost in politics.
Finally we have been incredibly slack at denouncing considered terrorist organizations for fear of loss of the immigrant vote - long supporters of the (ruling) Liberal party.
On the other side of the coin - this article was published in a very right-wing medium/by a right wing organization (Canada.com - a branch of Can-west - the owners of which also own the National Post - a very right-wing paper (although the owners are "Liberals)). All of the quotes and statements were made by one person with a political agenda. Furthermore there are increasing measures to control this problem thanks to American requests to tighten our borders for more efficient trade (if we don’t tighten our borders, then the US would clamp down on ours - killing trade).
My take is that there has been and likely still is a problem. Too many people here bring baggage with them when they come here. At the same time, many of these people are happy to be out of their previous “situations” and are not going to be too quick to start blowing stuff up. While we need to tighten things up, we need to be careful of painting all immigrants with the same brush - rejecting good prospective Canadians because of irrational fear (as, like the US - our country is built and continually being formed by immigrants).