Here is a rough dump on what happens when starting a sequence player.
UMovieSceneSequencePlayer::Play → UMovieSceneSequencePlayer::PlayInternal → UMovieSceneSequencePlayer::StartTimeControllerAndBroadcastPlayState → UMovieSceneSequencePlayer::UpdateMovieSceneInstance → FMovieSceneEntitySystemRunner::Flush → UMovieSceneTrackInstanceSystem::EvaluateAllInstances → UMovieSceneCameraCutTrackInstance::OnAnimate
Inside UMovieSceneCameraCutTrackInstance::OnAnimate FCameraCutAnimator::AnimateBlendedCameraCut is called, which calls FCameraCutAnimator::FindBoundObject to get the camera actor.
The FSharedPlaybackState state is what holds the binding object cache via its FPlaybackCapabilities Capabilities.