I don't know if this is true but I have heard in the past where rail replacement busses operate , some TOC s have used taxis to move their train crew rather than the busses mainly for the above reasons
Is true at my toc. We use a taxi, not a bus, as there have been too many instances of staff abuse whilst in uniform on buses. Plus TOCs know the buses are so unreliable that the trains will be late if drivers get them.