I think that I have mostly figured this out...
1. The first key is to get the bike bag/container weight under the 50 lb limit to avoid overweight fees. Most domestic carriers have dropped their oversize fees for bikes and will treat a bike as just another checked bag as long as it is under 50 lbs.
2. Someone please confirm this... After speaking with United it appears that the bike shipment policy is based on the first carrier's policy on the outbound flight of a single itinerary (outbound and return flight) booked at the same time. Note that the first leg DOES NOT apply to partner airlines! So even if you book on United and the first leg is on Lufthansa (a United partner airline) you will get stuck with Lufthansa's bike policy and (Currently $370) fee each way! The way to avoid this is to make sure that your first leg is actually on a United flight before hitting another air carrier for international.