Thanks for reaching out to Q&A forum.
You can run java apps/code in Azure Java functions. However IIB broker service is owned by IBM, so you might want to check with IBM if this service would be compatible with Azure Functions or not. If you have created your own node by using the com.ibm.broker.plugin and it is working as expected in your local machine, then you can deploy to Azure functions java runtime and then test it.
Hope this helps! Feel free to reach out to me if you have any questions or concerns.