The Greens have probably picked the worst time possible (for themselves) to do this. By far the main reason the SNP entered into this agreement, is to the get the budget passed relatively easily each year, instead of the normal excruciating negotiations they used to have to go through in the past. The budget has been passed for this year so the SNP have nothing to lose until budget time next year. I'm guessing that if the members vote to end the BHA, Harvie and Slater will resign and they may even leave the party. Wouldn't be surprised if they joined the SNP.