There is a preliminary REST-API available that can be used to fetch data and trigger actions.
The documentation is minimal at the moment, but the API-endpoints are listed in Sofie Core here: http://localhost:3000/api/0
If you're planning to build NodeJS applications that talk to Sofie Core, we recommend using the core-integration library, which exposes a number of callable methods and allows for subscribing to data the same way the Gateways does it.