Which is where many TOC's are vulnerable- their different coupling and control systems presumably prevent them from hiring in a few diesels to get the services going
Hired in from where exactly? Just how many locos would be needed to run even a skeleton service across the 3rd rail area? And what happens to all the freights that won't run as a result (at a time when road freight is potentially grinding to a halt)?
And that's without considering things like crew route and traction knowledge, DOO(P), etc.
It's a nice idea but it's just not practical these days.