Is there a time limit for providing the new info? It would be much easier and cheaper to show the new passport (to use the OP's example) at Champlain NY than to make a special trip to YUL. If the next time you crossed on I-87, if you told the US agent, "I need to update my passport info with Nexus", would that do? Or do you have to make a special trip to YUL within a certain time?
=aw