Actually I think the incident at the RBS has less conspiratorial origins, but turned into a handy PR coup for the cops.
I was not there, but from the various photos I've seen the police FIT team were clearly already inside the RBS building before any windows were smashed. The cops can't just walk in and out of empty buildings at will, so how did they get there? I think this is answered if you look back at what everyone was saying - this was the only building in the area without boarded up windows. And not only not boarded up, but with mirrored glass on the windows. Everyone has seen how cops use two-way mirrors on the TV to watch people without being seen. What are the odds then that this building was being used by the FIT team to get good street-level surveillance photos of the crowd without being seen? And that the last thing they expected was people coming in through the windows at them!
Meanwhile, the bizarre behaviour of the two or three unmasked nutters performing for the cameras gives the cops and the world's media everything they wanted from the day. Now, I'm not afraid to use violence or to encourage its use in the right situations (i.e. where it might actually succeed) but this stupidity overshadowed everything else and allows a determined police attack that results in the death of a demonstrator to be portrayed as an appropriate response to dangerous hooligans.
We should not judge our actions by the media's response to it, but I think this failed on anyone's terms. Double whammy.