In addition to the quarterly meetings, informal meetings and teleconferences are held among members on an ad hoc basis to discuss issues as they arise, such as assisting entities under attack.
The company only allowed its employees to discuss important matters during the scheduled quarterly meetings. 
mnli hypothesis: The company only allowed its employees to discuss important matters during the scheduled quarterly meetings.  premise: In addition to the quarterly meetings, informal meetings and teleconferences are held among members on an ad hoc basis to discuss issues as they arise, such as assisting entities under attack.