I beg to differ with sara007's post. I actually went down to the border last week. At first the CBSA officer was not familiar with the BOWP for CEC applicants but found the details after a few minutes. Unfortunately, my WP is still valid till June 2014. But he told me to come back in 8 month. ;D
Since the BOWP is pretty new, I will print the news release about the BOWP and take it with me to the border. It should work. Hey btw, it doesn't cost a dime to drive to the border and ask! Well, maybe the fuel, hotel, and all the stuff you might buy in the US does. ;D