After being nominated by the province, the province that nominates you will give you a work permit support letter. Remember this is different from the nomination certificate. I know lots of people from Alberta have problems with this because sometimes AINP didn't give work permit support letter but just the nomination certificate. So when they go to the border CBSA is asking for it then ask them to request the support letter from AINP. Then after contacting AINP they are asking for a letter who requested it.