When reading propertied on creation of new item in VSO not all fields are returned. Specifically we would like to see Target Date get returned. Here is the field type "Microsoft.VSTS.Scheduling.TargetDate".
Try and follow the below steps in case it helps out,
This worked for me for custom fields as well as other standard VSO fields. Hope this helps.
Forget "Custom Fields", it would be nice to just be able to get at all standard fields in a work item.