It seemed that most of the time companies using the codes would direct applicant to their main recruitment page.
I see QR codes being as effective as text campaigns for short term events like a large scale hiring event over the course of a month. I would use them to direct candidates to specific detailed pages that can offer information that was unable to be placed in the print ad (maybe include full positions lists or candidate requirements.)
In comparison with a text message campaign, the QR codes do not limit you to 140 characters. It would be interested to see what kind of detailed data could be retrieved from a QR code campaign. With texting, after the campaign runs you have the phone numbers of those that volunteered for information, is there anything comparable for the QR codes?
Here is another recruitment note about QR codes and Siemens' recruitment campaign: