If that is the case that access is restricted due to renovations, it would be good if CX gave a bit more explanation instead of a rather terse sounding 1 liner.
BA's lounge upstairs is indeed under renovation, but they've got a much larger, nicer one downstairs that they use now. And this one seems to be used only by BA anyway (it has a BA welcome poster, etc).
I've used it while flying BA in the last couple of months, but when I flew Cathay earlier this month, the agent gave me a pass only for the Clipper lounge, which is far inferior and crowded.
The BA lounge downstairs however, was shut at the time, since the BA flight leaves a couple of hours earlier!
It seems strange that Cathay hasn't negotiated to use this one, esp since the BA flight leaves earlier anyway, so no capacity constraint issues either!