ArriveCAN now is being used, I believe, in four Canadian airports for essentially customs and border services.
I recently came back from an international trip and used ArriveCAN voluntarily. It did help to accelerate my processing through the customs hall.
NEXUS is complementary. It, too, has benefited a great number of Canadians. We really hope that the American and Canadian governments can work together to make sure that the current disputes are resolved. There's now currently a backlog of over 350,000. They absolutely can work in tandem, and should. Until we get this problem with NEXUS resolved, we're not really at a point of discussing how the two can interact.