Program Support Unit (PSU) is a special department at the case processing centre.The PSU is a component of CIC's internal review centre. Applications are typically sent to this unit when CIC needs additional information from applicants or if the documents provided by the applicant need further verification. You will only be contacted by this unit in the event that they need additional documentation or information from you.
It was also noted that if a file is transferred to the 'PSU' the average processing time does not apply. They, in fact, do not have a timeline for files that are transferred to this department.
Unfortunately, any specifics as to why a file has been transferred to the Program Support Unit will remain unknown until a decision is made on the file, which as noted before, can take an indefinite amount of time.
In other words you can say it is like getting a RQ (many times another RQ) but not completely external (i.e. send to you for response) but mostly internal (verifications) and some times both.
Certain citizenship applications are also referred to this unit. Unfortunately like RQ once thrown in there is no way to find where the end is. Wait is the only answer you ever get from all quarters.
