Can the permissions of a service account in one project be passed down to a service account in another project?

edit

No, the permissions of a service account in one project cannot be directly passed down to a service account in another project. Each service account is unique to its own project and has its own set of permissions. However, it is possible to grant a service account in one project access to resources in another project by using IAM roles and permissions. This requires setting up a trust relationship between the two projects, and the service account in the first project must be granted appropriate IAM roles and permissions to access resources in the second project.