Node-red-contrib-google-cloud pubsub -- using topics from different project

We are using a node-red server in a different google cloud project than much of our other services. I would like to have some of our node red processes consume pubsub messages from a topic in one of those other projects. However, that does not seem to be a possibility. It looks like you can only specify the google cloud project as an environment variable on the server. But I can give the nodes credentials from different service accounts from another project.
node-red-contrib-google-cloud

Is there something I am missing? Can I get the pubsub nodes to subscribe and publish to a topic in a different project?

The only workaround I can come up with is a subscriber in the project hosting the topic that pushes the message to the node-red project either via http or a duplicative pubsub topic in the project hosting node-red.