Actually, both Canada and the United States have deported embassy personnel for taking detailed pictures of infrastructure like road bridges, railway bridges, dams, etc. If you are an engineer dealing with blueprints for stuff like that in the federal government, you typically have a "Secret" clearance. For your education, you should call up the government and ask for construction drawings, and see how far you get with that, because it is not going to go your way.

Yes, you can take down any building or bridge with a sufficient amount of explosives. The question, though, is whether it is one guy with a backpack, or twelve guys (which is much harder to pull off without being detected). And it is a question of where to place the explosives - that is very much a science. If you have the construction drawings, it makes it very easy.

And yes, you are completely correct that there are Chinese spies working in many Canadian companies. When I was working for Nortel, we would get visits from the RCMP and Canadian intelligence briefing us on the threat.

You really need to look a little deeper into the whole national security aspect of this.