The whole point of having emergancy plans is that they need to be able to cope with things going not according to plan. As such there should (as others have said about their experianses with other TOC's) be a set guide to state when and where each step should be taken. However doing simple things to cover for unforseen problems should be fairly standard.
For instance all fitters carry a crate of water bottles so if they can't fix it quicly there are at least some extra refreshments available for the passengers. Now I know that (for instance) 20 water bottles wouldn't go very far on a train of 500 people, but at least there would be 20 more bottles of water than there would have been. It may also be just enough to ensue that supplies don't run out (or if they fo at least not for very long) until more can get there.
With regards to the HST's doors not being able to open whilst alongside another train, you could get the rescue train to nearly alongside the failed unit, open two doors of one coach (manning those on the failed unit so no one other than a member of staff is in the vestiuble) move the two trains to along side each other (having moved the resue unit some 40m) so that the doors align. Then unload a number of people (proberbly about 3 or 4 coach loads) and remove them to a safe location. Then repeat, however as the train is less full it then maybe possible to do with 2 or even 3 pairs of doors to speed things up. Also the resuce unit could come with supplies to make it more bearable for those left on the failed unit.
With regards to the following trains and/or trains running the other way it could have been possible to have run a few of them the long way around whilst you undertook the unloading process.
For instance all fitters carry a crate of water bottles so if they can't fix it quicly there are at least some extra refreshments available for the passengers. Now I know that (for instance) 20 water bottles wouldn't go very far on a train of 500 people, but at least there would be 20 more bottles of water than there would have been. It may also be just enough to ensue that supplies don't run out (or if they fo at least not for very long) until more can get there.
With regards to the HST's doors not being able to open whilst alongside another train, you could get the rescue train to nearly alongside the failed unit, open two doors of one coach (manning those on the failed unit so no one other than a member of staff is in the vestiuble) move the two trains to along side each other (having moved the resue unit some 40m) so that the doors align. Then unload a number of people (proberbly about 3 or 4 coach loads) and remove them to a safe location. Then repeat, however as the train is less full it then maybe possible to do with 2 or even 3 pairs of doors to speed things up. Also the resuce unit could come with supplies to make it more bearable for those left on the failed unit.
With regards to the following trains and/or trains running the other way it could have been possible to have run a few of them the long way around whilst you undertook the unloading process.