Originally Posted by
swingaling
1. Which line are you referring to? Line 18? This
map of the planned subway system is pretty interesting; it's from 2015 so already a bit outdated.
The high speed train.
2. I could see it happening in separate ticket situations primarily.
For instance, let's say you want to get from the US to ULN. If traveling on AA, one would enter china at PKX then need to get to PEK to catch a flight to ULN (either on OM or CA). ULN isn't a high volume route, so I doubt there's enough demand for CA to operate flights from both PEK and PKX. Presumably, CA would use their PKX slots for something else.
If I wanted to go to ULN, I would be sure to connect in PEK or ICN. While I don't doubt that we'll see threads here from people who want to transfer between the two airports, I'm quite sure that there will almost always be ways to avoid this drill.