In episode 139 of the weekly Hump Day Hangouts by Semantic Mastery, one viewer asked if it feasible to promote a video that is already uploaded on someone else's channel.
The exact question was:
Also how does this work if another marketer has it up on that marketer's channel but they don't want to take it down or the client does not want to ask the other marketer to take it down? Is it feasible to promote a video already up on someone else's channel instead of putting it up on your own channel. I do strongly prefer the control of having it on my channel.