These are conversions that were seen at Warhammer Open Day in the display cases. While they are said to be made out of a Stormsurge model, they are rather cool. Combine them up with some Forgeworld Tetras, and it they could look good on the field.
Just a few fun things to check out on Sunday Afternoon.
Here is a comparison of the Forgeworld models
Here is the original video they were in made by sinzaren. The Tau Conversions can be seen at 9-10 seconds in.