Cont...
Why do power stations require input power to start generating?
Some can but most can't for variety of reasons. If the place is dead totally there is no power to start anything with,such as open motorized gas valves,run cooling pumps, run or monitor protection devises ,meters etc. excitate the generator field windings it just sits there as one big block of useless concrete and steel.
Why do they take so long to spool up?
They don't really, Torrens Island has I believe 6 generation sets. They would start or stop them as the load demands. While there is some lead in time required to say get them running they can see demand rising on their monitoring load meters etc and so should be ahead of the game for normal increases. I include your eastender effect scenario in this.
During periods of increased demand does this extra load cause the generator rpm to decay? No because it isn't allowed to. If the load became so great and all sets were running at maximum, load shedding would start occuring. Usually by turning off some suburbs for 1 hour each in rotation which has happened before in Adelaide. If load shedding was not carried out the protection devises would start disconnecting as happened with the interconnector.The rest of your question is answered in part 1
Why are the back up service providers secret?
I have no idea either and it is a disgrace!
Hope I have given you some worthwhile info be it in very simple terms.