Interesting thing I've never thought about that goes on for those transferring to other teams.
EF Education send termination notice to Sergio Higuita after early bike switch
Apparently he didn't ask permission or those of Team EF actually at the race didn't think it important enough.
Although the article says that it goes on at races with lesser media coverage. I tend to think that it shouldn't go on at all so one doesn't have to rely on a judgment call as to when a race has sufficient media coverage to be important to a sponsor.