I don't know about the neighbourhoods being predominantly Muslim, there are more offices than residences there, I think, as the locations are in the City centre; but certainly a number of Muslims live and travel through them. There is an Arab cafe at King's Cross for example, where some of the victims received first aid, and all the customers helped out. The racial/religious distribution among the victims is not known, but judging from the pictured of victims that I have seen there is a big representation not only of Muslims, but also Hindus and Buddhists, as well as Christians of various denominations. London has a very multicultural community, and this seems to be reflected amongst the victims.