I just flied KHH-HKG-SYD yesterday. HK express + CX.
I bought KHH-HKG and HKG-SYD as two seperate tickets but HK express still interline my luggage to destination, sydney and issued two boarding passes for me, amazing! The two boarding passes were printed with HK express logo and there was no any CX membership number/status on them.

After arriving in HKG airport, I went to transit area to ask CX crew reissue me a new CX boarding pass and lounge invitation. I also requested my luggage to get first class priority and surely she was happy to do that for me. When arriving in the Pier business lounge, the crew lead me into a special area exclusively for DM where la carte and wine list were provided , just like the Pier First lounge before . This was very nice surprise.Well, the la carte was so so but wine list was better than the Pier First lounge used to be. There was one champagne in 2009 which used to be served in F class FRA to HKG.