Communicate with integrated Bitbucket from JIRA Cloud

I am developing an add-on for JIRA Cloud. This JIRA is integrated with another instance of Bitbucket Server via Oauth.

Is it possible to communicate with Bitbucket from JIRA Cloud taking advantage of the already made integration?

I’m going through the documentation and I’m a bit overwhelmed. I’m just thinking about making REST calls to Bitbucket Server (cross domain…?), but there must be a better approach.

Could somebody help me?