Alrosa main rough sales are a fixed price, similar to DeBeers...

Alrosa main rough sales are a fixed price, similar to DeBeers and Rio, the tender in Israel is probably online auction format.
The three large suppliers have fixed sales dates and customer base. Each customer will be offered a selection of goods at a fixed price, they can reject the box though they run the risk of being delisted from the customer base!
The boxes offered to each are based loosely on the requirements of each customer though likely to include stuff they may not want, this would then be extracted and on sold mainly in Antwerp or Dubai.