since DL does not have a 717 base east of ATL/DTW, repositioning pilots via MCI/SLC/LAS consumes a lot of pilot time. DL does not 'leave aircraft' or pilots separated from their maintenance and crew base, if that is what you mean by firewalling.
when DL first considered 717 service from LAX, the idea was to use the Texas-LAX routes as a bridge. MCI could be one but it is a longer route.
Also based just on the number of flights mentioned/ (PDX and LAS), that is several crews worth of 717 flying per day. there has to be multiple bridges or multiple frequencies per day on that bridge.
we can detour to the 717 discussion but the discussion is about DL's growth of LAX to Asia and I said and it is now apparent that DL will add capacity to LAX and will protect its LAX to Asia franchise and grow the domestic system to do so.