That's a really important point actually, and possibly the biggest condemnation of Privatisation.

Although productivity under BR was pretty poor in many areas, at least most crew could just jump on a waiting train and take it out. It was usual for traincrews to work ALL types of traction at their depot and have enormous route cards. As they progressed through their careers they clocked up more and more knowledge.

You now sometimes have a situation at a major location where there are many drivers and guards present, but NOBODY can work a train because everybody only signs the little bits their own company needs.

To move that train they MUST;
1) sign the route
2) sign the traction
3) work for the TOC/FOC which operates the unit.

Most crew usually have 2 out of the 3 criteria, but sometimes not all 3.

So the train stays where it is until the company concerned chases down a Rest Day crew member and taxies her/him in from 50 miles away.

Best wishes, B W

As a matter of interest, in the airline industry (my work) there is almost always a crew on standby, either on home reserve (must be contactable and able to proceed to the airport within a set time period) or on immediate standby at the airport. Mobile phones have made reserve much less restrictive.