After surgical pleurodesis can a pneumothorax still happen?

Yes: Not all pleurodesis are the same. Depends on the agents used, the method of application, and the nature of your pathology, the success rate varies greatly.

Yes: As noted by drtsai, there are different techniques. On average, a vats pleuradesis that uses talc application has over 90-95% success rate in primary spontaneous pneumothorax. This means, there may be up to 10% of individuals, even after aggressive surgical and chemical pleuradesis, that have recurrence.