I can assure you that the gate agents at ZRH will be blissfully unaware of any CTA rules and will not care about them in the least. They will apply the LX carry-on policies that you have discovered.
Note, though, that enforcement isn't uniform. It depends on the aircraft used and flight load. I've both seen people getting away with very large and heavy carry-ons, and at other times gate agents using scales and frames to diligently enforce the policy.
Should LX agents indeed force you to check your bag and make you pay for it, you can always take it up with AC to reimburse you. But I wouldn't hold my breath.