In a Bus topology, all transceivers connected to the same bus can "hear" each other. This means that they are all a part of the same collision domain. When transceivers transmits something on the bus, the others have to be quiet to avoid a collision.
An example of this, is the old Half - Dulpex Ethernet, that used coaxial cables to form a bus topology, with CSMA/CD to avoid and cure collisions.
With that in mind, I think that the correct phrasing is that the bus is occupied while there is still data on the line, regardless of the receiver. Note that I say "data on the line" instead of "while data is being transmitted" since the data remains on the line for a while after the initial transmission due to propagation delay.