I don't think he is, I think scylla is. The question wasn't addressed to her so what is she telling stories about her vacation for? Nobody is answering his question and I'm interested too. I don't have a US visa and I don't want to get a decline from US oficer. Also I don't know what would happen if I got a decline from US and than some problem with a new work permit occured? Do I have to physically leave the canadian soil or not necessarily? Is there a crossing where I could only talk to Canadians, but not to Americans? Anyway St Pierre and Miquelon seems to be a good option so if anyone knows how it works there please share.
If you don't have a US Visa (and are from a country that requires one), and you present yourself to the US border, then you will be denied entry. If you present yourself with the specific aim of flagpolling then you will receive an administrative refusal. I understand that they used to give a piece of paper detailing the administrative refusal, which you presented to Canadian authorities, although recent reports seem to say that they're not longer issuing this.
If you have status in Canada, a valid visa, then you should be allowed entry back into the country, even if the Canadian authorities do not process your work permit or there is an issue with it.
A border crossing is between two nation states. There will be border agents from both sides present. There is no option of not speaking to a US officer.
Basically, only flagpole if you have status in Canada. Additionally, I would only recommend it if you needed the work permit quickly. Online applications seem to be taking around 2 months to process at the moment and you can legally work while the application is being processed, if you have maintained status.
Good luck.