Even though the file has an extension of BIN, it has nothing to do with Daemon Tools or virtual ISOs. If you open the file with a text editor, you can see this: Attachment 63311
It is actually a list of MapObject links. It is used for one purpose only – populating the map editor with objects. If you have a clean ToE installed and delete all its index.bins from data.pak and a2-data.pak, the game and editor will still run without a problem; RMG will still be able to generate a map, but the editor tool panel will be empty: Attachment 63312.
Long story short – after some research – index.bin is actually a database built on Microsoft SQL Server 2000 Desktop Engine back when the game was made – so maybe it can be opened with some kind of DB tool, but my knowledge here is limited.