For further understanding pls read CIC manual http://www.cic.gc.ca/english/resources/manuals/op/op06c-eng.pdf
After PER and creation of GCMS notes CIO sends all files to VOs. After that, CIO assesses SELECTION CRITERIA. VOs only make practical job:as sending MRs, passport work etc. VOs only check authenticity of docs and probably randomly or for selected candidates.
VOs will do security and criminal check.
This what I believe is that VOs wait in queue in CIO for assessments of their apps. Thats why CPP-O had a break, because CIO worked on NDVO apps. In time when NDVO send MRs, probably CIO is doing assessments for another VO. Probably it can be London and other less occupied VOs.