When my itineraries cross airlines like this, I try to get the operating airlines' PNRs and update seats manually in each of the records. Otherwise the risk of getting the worst seats on the interline downstream flights rise substantially -- more so if the airline checking you in can't issue or doesn't issue boarding passes for all the connecting flights too.
In the US, UA and DL also often just drop the bags at the door of houses, sometimes without even knocking or ringing the gate/bell. They contract out these things to get the bag to the doors/hotels; and sometimes (actually very often) multiple airlines at a given airport use the same contractor for these deliveries and so there is no noticeable difference between the carriers in this regard.
Last edited by GUWonder; Feb 22, 2015 at 2:45 am