The decision was voted in by Labour and the Tories, with the Lib Dems voting against (they want the trams to go to St Andrews Square, in the centre of the city), with the SNP abstaining (because they've always been anti-tram, and have washed their hands of the whole thing).
Today, it's transpired that because the tram line isn't going to deliver what was promised, the Scottish government (SNP) are going to withhold the final £60m of the block grant they were contributing.
The previous decision by the council wasn't something that could be reopened - unless something happened which materially changed the consequences. The withholding of the grant does that, so there's going to be a special meeting on Friday.
At which, if I had to make a guess, the SNP will say "You lot couldn't organise a piss-up in a brewery" and vote in favour of the trams going to St Andrews Square, thus looking like they sorted out an intractable problem, and stopped Edinburgh looking more stupid than it already did for the constant stream of tram-related fuckups over the last few years.
I wonder if they had that planned all along.
Edit: Oh for fuck's sake. They'll also have to hand back £5m and write off £20m of contributions made by businesses on the grounds that the trams would go past their front doors. More here.
Original post on Dreamwidth - there are comments there.