Saw this and couldn't help but comment (incidentally I'm not directly involved with any of the parties) - just speaking from the point of view of having a bit of background knowledge and experience:
A couple of points to consider:
1) Do you actually want anything like this to happen in the area soon (i.e. before 2011)? (I'd actually say - possibly no here - reasons will become clear later on)
2) If you do want something to happen (which I get the impression ERG does) did anyone consider that TfL/Lambeth may have a limited window in which to spend the money (i.e. Ken gets re-elected next year which may effect TfL budgets in the short term - who probably bankroll through LIP's about half the traffic departments for boroughs in London due to the far reaching effects of the network). The Central Square is in the first tranche of the "100 Public Spaces...." projects, Lambeth went red last May - lot of political issues involved - which may limit the funding windows (as both the highway and square projects have to be well into 7 figures from looking at plans, plus the living landmarks funding mentioned in the Standard last year, which would mean well into 8 figures is allegedly supposed to be scheduled to be spent on Brixton in the next decade). 2007 approval for 2008 funding is key, as I'd guess 2008 approval for 2009 will be limited.
3) If my thoughts on 2) are right (they could be wrong) - maybe the consultant hasn't worked the traffic model out yet and because of the tight programme they having to push a planning application through - and then change it (to what the library exhibition showed) once they have the application in (i.e. despite the consultation some years ago saying that residents would like the ability to close Effra - for the last two years as far as I am aware a scheme like the one mentioned above has never been on the cards? - it just wouldn't work with the road layout and volume of traffic - think about it!!!!). The only way something like the bus idea stated above could happen would be if someone with no idea of the concept and political levergae to pull rank or a landscape architect was calling the shots (if that's the case - good luck)
4) The reason why I would say no to 1) - the Cross River Tram project - if all this money (as per 2)) is being spent on highway projects but the Cross River Tram may terminate down at St.Matthews in a couple of years (hence affecting the square and highway projects) why take the risk of wasting money and having to rip out what you've just put it? (okay the argument is probably that the money probably won't be there come 2011 - as per 2)) - I'd just be thinking of the public inconvenience. Cross River Tram has to end up at St.Matthews (or otherwise people's front porches in Pope's Road will end up getting the low floor treatment and becoming a tram platform) - Pope's Road cannot happen - it's not feasible. The reason why it probably will is what may happen south of there in the coming years. TfL will probably have undoubtedly thought of this and should be able to tweak the designs - you just hope that someone makes the right decision. It's a question which needs to be asked (it's too late to ask when someone has stuck something in the ground). My thoughts would be if you make Effra bus only and one way southbound, the tram would have to terminate in Brixton Hill (due to lack of space) - where do the cars go and the 100+ northbound buses per hour????
Sorry for the rant - needed to get it off of my chest and just hope the people this affects make the right decisions and ask the right questions.