Under the DIAC rules Student Visa holders (aviation related or not) can apply for the right to work for up to 20 hours per week..and this is usually granted. Indeed many students outside aviation do work to help fund their drinking money at weekends!!!
That is true, though I don't think any actual CX cadets would have the need for part-time employment outside their training. Doing a CPL, ATPL subjects and MECIR within the span of 1.2 years is probably enough to keep them on their toes!
While the CX cadet program has been opened up to international applicants with all sorts of experience, it does occur to me that some facets of the program have not been updated or improved along with this change. As a result the loophole on "free training without obligations" comes into existence. This problem did not exist when the CPP was restricted to HKG locals - I mean, with their cadet training done, where else could these locals find jobs, except with CX? I wonder what Cathay have done/will do to address this problem. Perhaps getting people to pay (a deposit) for their training would be a solution? Who knows.