Couldn't find the value of cusmom fild in RRDI
One answer
I suspect this is because the reportable rest api does not support "complex" custom types yet. This enhancement discusses adding Contributor type custom attributes to the api. You could add a comment there that Iteration types are also required
https://jazz.net/jazz/web/projects/Rational%20Team%20Concert#action=com.ibm.team.workitem.viewWorkItem&id=184675
https://jazz.net/jazz/web/projects/Rational%20Team%20Concert#action=com.ibm.team.workitem.viewWorkItem&id=184675