The report of the 7 July Review Committee has published it report examining how the multiple bombing in London were handled. It is available at http://news.bbc.co.uk/1/shared/bsp/hi/pdfs/05_06_06_london_bombing.pdf
It states that one of the main problems was establishing exactly what had happened. There was very little communication from underground, where three of the bombs exploded, and much of the initial information was conflicting. Even once it was established what had happened, establishing the scale of the incident was very difficult. This was partly due to a procedural failure where each emergency service declared their own emergencies at each scene, whereas the first declaration of an emergency should have applied to all the services.
This seems fairly typical in my experience of emergency management. There is a general reluctance to declare an emergency. Although people do tend to start following the emergency procedure, the lack of formal declaration often causes delay and confusion.
I also wonder if a single command centre for all the emergency services would have been more effective. There seems to be political problems with the emergency services working together, which are simply beyond me. We want a combined response, and them have seperate control centres does not seem to help in any way.