The application process to determine eligibility takes approximately four to six weeks.
Once the initial processing of your application is complete, you will receive a letter indicating whether you have been conditionally approved. If you have been conditionally approved, the letter will contain an invitation to schedule an interview at a NEXUS Enrolment Centre. Once you have completed your enrolment interview, a membership card will be mailed to the address listed on your application within two weeks.
http://www.cbsa-asfc.gc.ca/prog/nexus/application-demande-eng.html