1. It seems unlikely that all the students were conspiring except one. Why leave one student - and exactly one - out? Was s/he incredibly unpopular? Did s/he have minimal contact with the others? I suppose it's possible, but it's also quite strange.
2. It seems unlikely the students didn't understand that if the schedule was random there was a non-zero chance of non-cheating Student 1 doing the admin.
3. It's more likely the schedule was posted ahead of time. Given that, it seems unlikely that anyone would be surprised or flustered when the schedule went as scheduled and the alleged plan failed.
4. It seems very unlikely that the keys would literally be chosen out of a hat. IME of these kinds of exams there's no need for randomness. Students tend to be asked for the less familiar keys because they're less likely to know them well. If someone gets C major and someone else gets Gb major for random reasons it's really not much of a fair test.
5. It seems quite unlikely that a student would be asked to hang around and do admin for an entire day - especially when the admin is essentially trivial anyway.
6. It seems unlikely that anyone who could play the short and long pieces well would be completely put off by being asked to play a scale they hadn't practiced.
7. It seems unlikely that a student would literally say "Oh we didn't practice because we wanted to spend our time partying and dating." That sounds like something someone would say about students, not something students would say about themselves. (This isn't about whether it's true, but whether someone that age would use those words.)
To be clear: this isn't about defending cheating. I just find don't this story very plausible.
Also, the irony that this article about cheating may be somewhat elaborated isn't lost on me.