Is it common after carpal tunnel surgery to get trigger finger?

No: No not at all (if it's true trigger finger). However you should make sure there is no scar tissue adhesions in the carpal tunnel that may be "tugging" on you flexor tendons and giving you the impression of trigger finger...

Yes: There has been new research demonstrating an increased risk of trigger finger after carpal tunnel surgery. The release of the thick ligament which is causing compression on the nerve does alter the biomechanics of the tendons slightly which can increase the chances of developing trigger finger. This article was just published within the last few months.