The Adobe Experience Manager team said that this use case was not an out-of-the box supported AEM feature and therefore not documented.
While its true that you can post data from a Ruby on Rails application to Adobe CQ using a SlingPostServlet:
https://dev.day.com/docs/en/cq/current/developing/sling_cheatsheet.html
What you are asking is different.
The answer from the AEM team regarding your question is:
"I don't think this is likely to work without a fair bit of effort. Rails-on-JRuby is mostly focused on running on existing JavaEE web containers, not OSGi."
The only real way to get this to work is to get Adobe Consulting involved. This use case will require engineering modifications that can be carried out by the AEM consulting team.
Hope this answers you question.