I heard that the rumours coming out of the BCB were that they were concerned about being "alone" if they didn't vote for it...
THe way I see it is that if it is going to pass; then the majority of the boards who are on-the-fence will vote for it and you'll have CSA and the PCB as the only ones against it.
The way I see the votes going as of now are:
YES: BCCI, ECB, CA (of course), WICB (they've pretty much said that they support it; plus India have been... quite kind towards the West Indies recently and perhaps they don't want to lose that?) and the NZCB (similar reasons?)
NO: CSA (the board that loses the most from this; definately hasn't been treated very well by the BCCI and sees itself as oneof the big nations in cricket while the proposal ignores them); PCB (I'm sure they've came out against, haven't got a source though)
At this point, its 5-2 towards yes. If its a simple majority, then they need one of the remaining votes to guarantee a win (unless the tiebreak would go for the proposal, I'm not sure how its decided). If its a super majority; you'd be talking about 2/3s normally, so that's 7 boards.
Those undecided currently are SLC, the BCB and the ZCB - the three nations most likely to lose out from this proposal. The grapevine seems to be saying that Bangladesh my vote for the proposal while not really liking it because they need the 1 ODI every 5 years from India to survive, which would make it 6-2 (a simple majority). God knows that the ZCB will do, but I'm guessing that they'll go with South Africa on this, especially since the "Big" nations probably won't be touring Zimbabwe any time soon and there won't be any ICC competitions for a while, so the cuts in revenue sharing would actually hurt them.
Thus, if my assumptions on the voting system and the attitude of the boards are correct; its all down to how Sri Lanka vote. I dunno, but I'm not feeling very optimistic...
e: Personally, I think that they should give the associates representation in ICC decisions. Perhaps not too the level of the main nations (it'd be dumb to give Jersey and France the same voting powers as India), but at least some protections to ensure that they were being listened too. Perhaps all decisions would need 50% of all members and 50% of full members; with big ones needing 2/3s of both? Perhaps state that associate/affiliate members have to approve ICC funding proposals, with any cuts not going through unless approved? I dunno, but a more independent, inclusive ICC would be much better for the development of the sport as a whole rather than simply including India in the old Australia/English duopoly...