I noticed that _ca alpha textures (dxt5 compression) with supershader will not be affected by shadows at all. When _co alpha textures (dxt1 compression with alpha) are used they receive shadows. However, the dxt1 compression only allows 1 bit alpha, which looks very poor.
This improvement would enable us to make much better looking track textures for tanks for example, similar to the way they look in WarThunder (by utilizing multiple stacked layers of alpha textures). The 1 bit alpha maps just look too poor for this to work properly.