For anyone who hasn't watched the previous series', they are all on iPlayer at the moment, well worth a watch as there are references and links to the earlier ones.
https://www.bbc.co.uk/iplayer/episodes/p00yzlr0/line-of-duty
I wondered about them not getting out of the cars and no casualties but wondered, either if there is a gang of police in on it, a bit like the female officer who was shot in the first episode talking about others on the take. Or, it was some kind of set up from the police, side of things as a potential target (or manufactured to be one).