Yes, I guess it could be considered hackish if it is a solution not standard in one or the other framework so you are correct.
Read this about CDI and Spring http://java.dzone.com/articles/why-cdi-won%E2%80%99t-replace-spring
. I think, at least for me, shows why you may want CDI and Spring in a single application. Granted, I realize normal architectural principles would make it seem not likely you have your JMS code and JSF code in different layers. But, I have done exactly as shown in the link. I had my Web application using JSF for the presentation and portion of its backend functionality involved posting to a JMS queue. As the author states, Spring makes using JMS almost trivial compared to the alternative.
So is this a reason (or use case) where you would use CDI and Spring together?
I really wish someone could jump in who has gone down this route but any users of CDI I have talked to have started using it now and were not users of Spring anyway so they are not having the conflict we are having!