Well...had a ex-CX guy in the flight deck couple months ago and he said CX did go after him, along with the IRD. He managed to drag it out for 3 years but in the end, he paid up! Both to Cathay for lack of notice and taxes to the IRD. The state that he lived in somehow has a "thing" with Hong Kong making contracts signed overseas enforcible.
I left without the 3 months, so far CX has only threatened me by emails. Haven't received anything else. Keeping my fingers crossed.