Talk to TNVisaExpert, he deals with these kinds of problems all the time, we can make suggestions such as using a Canadian address on the I-140 but I'm assuming your employer will want more than a suggestion.
I tried.....it did not go through. I tried contacting an Admin (Canuckabroad) about it but I was unable to write on his wall. Maybe I am doing something wrong.......
I'm sure he has his own website somewhere, the last one he posted though I seem to recall he took down. www.tnvisaexpert.com is a website, not sure if it's his though.