Originally Posted by SilverChris

You'll need the onward boarding pass for HX to be allowed up to departures. This sounds like a separate ticket, so you'll have to hope that HX gives you a mobile/self-printed boarding pass (I'm not familiar with that airline). If they don't, or if it isn't accepted by the staff for transfers, then you'd have to head to the transfer desk for the physical BP. From that point on you'd be considered an "unclean" arrival and be subject to the regular transfer security check.

From what I've read, only arrivals from the US are allowed to bypass security for now.