A rail union has warned that millions of pounds could be "wasted" while the future of the West Coast railway line, which runs through Milton Keynes and Northampton, is decided.
The Rail Maritime and Transport union said the fate of the West Coast Main Line had become a "fiasco" after Virgin lost its franchise to the First Group.
Sir Richard Branson's company has launched a legal challenge to the Government's decision, but a date for a hearing has not yet been set and the franchise is due to be handed over on December 9.
The RMT said it understood the trains could be painted grey while the legal challenge is heard.
General secretary Bob Crow said: "The Government are prepared to blow £5 million on a temporary West Coast rescue plan rather than giving them the opportunity to simply get on with the job - another classic waste of time and money by the Government in pursuit of their failed rail privatisation policy."
Government-owned Directly Operated Railways could run the route until the saga is resolved.