If one considers that the 'dog attack' incident to the north end of Royal Exchange Buildings and the Tomlinson assault to the south are connected by a number of police personnel and a short period of time (ie that some of those at the 'dog attack' then dash down the path to the location where Ian Tomlinson is then assaulted, all in a short space of time), then it would appear that the police officer who actually batons and pushes Mr Tomlinson talks to or takes some form of instruction from one or more police officers in the blue flashed hi-vis jackets before moving off from the 'dog attack' incident - as do other officers in the group we see in the assault footage. This might indicate, we may speculate, some level of command or control.
(This is, I note again, only speculation. Perhaps there were a number of left-handed baton-wielding riot cops with no epaulettes, high cut hi-vis jackets, balaclavas, trousers tucked into their boots, Nato helmets and no shields running around the Royal Exchange area of London between 7:16 and 7:20pm on the 1st of April. Hopefully they will all be making formal statements to account for their own actions and to bear witness to what they saw.)
As the evidence is assembled and analysed it may well be possible to piece together not just a chain of events, but the reasoning behind it, right down to who said what to whom at what point.
Before I forget: A LibDem MP (IIRC) raised an interesting point recently, suggesting that it appeared that the police were operating a 'designated hitter' system during the G20 protests.