I would say as grow out tanks for fry they could work very well. As for separating adult fish I am not sure because most bins tend to have irregular shapes (for handles) and tend to slant inward as you go down, meaning the top of the bin is wider than the bottom. The problem I see here is getting the right type of divider to match the slight slanting but you could also use Plastic Canvas which works pretty well and can be cut to shape and size pretty easily.
You would also want to make sure that the bin is made of a nice thicker plastic than the typical storage bin you find at target/walmart. These tend to bend with the weight/pressure of the water over time causing the lid to not fit properly or at all. So if you do consider getting a bin I would say your nearest Home Depot/Lowes would be a good place to check out as they may have more regular shaped bins that are made more for holding tools etc, and better quality plastic.
Also for the heater you'd probably want to make sure the heater has a protective cover to keep it from coming into contact with the plastic bin.
It would be really cool to see what a sorority would look like in an all black bin with floating plants etc. Would look a lot like koi in a pond but the mini version. >>>Bettasusa>>>>Gets Ideas...LOL