The individuals attending the lab would have attended as temporary visitors under the policy at the time, which required them to be escorted if they were in the lab. They were granted access because they were not going to be in any part of the lab that was secure or required a clearance.
Evidence of meeting #38 for Canada-China Relations in the 44th Parliament, 1st Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was policies.
A video is available from Parliament.