Nephew received AOR email with UCI and Application # acknowledged application received on May 22/18.
How applicant/sponsor would know which VO is file transferred? I think they will send another letter indicating it.
You might want to post questions to April 2018 group.
If your nephew’s application was received in April and AOR1 in May
You will be able to see where people who applied at similar times are at with their applications and they can help you more.
But from my knowledge from the forum, they will update GCKEY and send an email to principal applicant with this info generally 2 weeks or less time after principal applicant receives medical request however sometimes if the application stays in Mississauga, some applicants have actually not been receiving VO emails, but there will be an update in online account saying background check in progress