Use ECS backend in WEB frontend

I'm using traefik wihth the ECS provider which creates frontends and backends for me.
Is it possible to use the backend created by the ECS provider within another provider ?
I created some other frontends via the REST plugin and i was not able to reference a frontend to a backend created by the ECS provider.

With the v1 that is not possible. The v2 makes it possible to reference accross providers