I suspect that the council is more concerned with which mix of options will save money
That would be reasonable. What really worries me is that the council are being driven by being seen as low on the list of recycling, when they may actually be doing really good work by generating electricity.
It may be that rural councils which have resisted incinerators are being rewarded, while Lewisham is being penalised for actually having an incinerator that does good (although I've heard that the Combined Heat part has never actually been operational to heat local houses, so it isn't quite as efficient as it could be). Or it may be that policy is being determined purely by positions of league tables rather than the reality of waste disposal in the borough.
Unfortunately as the answers given to Samuelsen show, we are unlikely to get a straight answer from the council or anybody else.