I tried that and it didn't work, plus many other variations. But ~I did find a fix just now. It seems you have to set the entity's alpha to something other than 1 for alpha maps to blend. This sets the maximum opacity for the alpha map.
Setting 'EntityAlpha entity,0.999' basically turns on alpha mapping with colour mapping correctly, where alpha = 1.0 is opaque.
Setting 'EntityAlpha entity,0.5' limits the alpha map to half opacity maximum.
Setting 'EntityAlpha entity,0.999' basically turns on alpha mapping with colour mapping correctly, where alpha = 1.0 is opaque.
Setting 'EntityAlpha entity,0.5' limits the alpha map to half opacity maximum.