How do containers with different priority labels get routed?

For context, I'm working on the integration between Dokku and Traefik. A single deploy may start one or more web containers that are routed via Traefik. If a new deploy comes up with newer rules - and consequently, a higher priority - are the old containers that have the same "matches" still routed to but via the new rules, or does all traffic on those matches go to the new containers?