There is no safety reason why rail replacement bus services cannot run tomorrow. The storm is over. They won't be able to serve everywhere due to flooding, but that is no reason not to serve the places they can.
No safety reason. What little fantasy world do you live on ?
Megabus and National Express probably shouldn't be running, their own foolhardy behaviour is not an excuse to berate Virgin Trains and others for refusing to run rail replacement bus services.
We've got roads washed away, bridges which may be unstable and liable to collapse, bus and train stations without electricity, and to top it all, we've got rain coming in tomorrow, and again later in the week, which will add between 80mm and 100mm of further rainfall on already saturated ground.
If the WCML opens this week at all, it'll be something of a miracle, VT will get some sort of replacement bus service up and running when it's absolutely safe to do so, but telling people not to travel at the moment is the most responsible course of action as well as the most sensible course of action for the railway.