IBM BPM has data-redirect.jsp in the /teamworks context root you can pass in the csv data as a POST via a form and it will output an excel file as download.
To convert a BO list into a csv format you can use the out of box XML+XSL transform service available in system toolkit.
In the attached example I have created a xml transform to csv using xslt and then bound it to a export button which has the submit form in it and passes in the csv data using config variable.
It is a generic approach and any BO list can be transformed this way.
https://bpm.tips/?qa=blob&qa_blobid=13183627047551441287 (IBM BPM 8.5.5 example)