I recently just learned about this app, and I'm travelling home for Easter.
Previously it didn't let greencard holders to use the app, and now it does. I'll be travelling through the airport in Montreal, and its in their list of available airports, so thats not a worry either.
It didn't make me scan the card at all, so I was wondering what happens once I hit submit when I get to the airport going back home(USA). Mostly wondering to know if its just easier to do the regular customs line than have a hassle in the MPC line is all.