Sometimes, yes, and sometimes, no.
I think kwvr45's point was that EC, or any other well-stocked operator has much more scope to provide a replacement at short notice, and at a useful location.
By way of example, an EC HST developed some power car problems on the Inveness run a couple of weeks ago (driver noticed leading PC cutting out occasionally. Even if the PC developed a permanent fault, it could have managed to keep going at less than 125mph, but timings would have begun to suffer as the day progressed. He reported the issue and control planned a solution). EC were able to provide a full replacement HST to pick up its diagrams and they planned a swap on one of the double length platforms at Waverley.
Not only did EC have the right stock available in the right place, but they even managed to have duplicate seat reservation tickets ready in place on all
seat-backs. Passengers were all advised of the simple transfer to an identical train set a short walk down the same platform with staff ready to assist.
Now there's a great deal of work required to make these seamless swaps work, and no further time was lost during the swap, but the crucial difference is nothing to do with franchisee vs open access, nor one company vs another, its simply having enough stock available ready for service.