I don’t think this is right. The flight must be operated by CX and OP is talking about taking CX flights.

It is my understanding that Silver gets you access to the lounge officially used by CX at the respective airport you are leaving from. This could be a CX-branded lounge or it could be a contract lounge - whatever shows on the lounge invitation card. The website certainly doesn’t specifically say this benefit is limited to CX’s own lounges although it doesn’t say otherwise either.

On the flip side of this, you would not however have access to the CX lounge in HKG for a BA flight to London, nor to the QF lounge in HKG before a CX flight. These would require OW Sapphire.

Does anyone have direct knowledge/first hand experience?