Is it possible to change the owner of a change-set?
Accepted answer
As you indicated in your question, what you really want is to remove the restriction that you can only associate a change set to a work item if you are the owner of the change set. Changing the owner of the change set is just a way to workaround that restriction. Removing this restriction is requested in work item 57870 https://jazz.net/jazz/resource/itemName/com.ibm.team.workitem.WorkItem/57870, and work on it is being tracked in story 219256. That work is currently tagged as scmrun401candidate, but it is not currently marked as in plan, so it probably wouldn't hurt for you to add a comment to one of those work items, indicating your interest/support.
One other answer
No there is not a way to change the owner in the normal developer workflow.
For import workflows (svn import, etc.) administrators can impersonate users to have the change sets they import be associated with different userids rather than their own.
JohnC
SCM Lead